I get infinite loading on changing cell(exterior to interior, or interior to exterior, fast travel). Sometimes It instantly crash to desktop with out of memory message. I opened task manager and I saw FNV memory usage, and it stays at 2500~3000mb, even I installed 4gb patch, it is too much for that game hold. I don't know what is the problem is. Should I reinstall the game?
sorry for my bad english.

I had that problem and 4gb patch helped a lot. I would recommend reinstalling 4gb patch in case it was incorrect. After that install NVAC (New Vegas Anti Crash). That should help out your crash issue.

How many mods are you running? If you have too many mods or maybe too many mods that override each other, it can result in sever game instability. When push comes to shove, you can always reinstall all the mods, and if that doesn't help, than try to reinstall the game. I know that can be a huge pain but it may help in the long run.

I hope this helps. I hate it when my game does that, and its even worse when I can't find the problem.

I'm assuming you're using mods @panstone? Do you have these issues when you disable all the mods? Also what are you PC specs?

Well the thing with New Vegas is that it really doesn't cope well with high resolution mods, even printerkop said this before (if my memory serves me right, he really said it). The 4gb patcher could help though, but don't expect it to do a really fine job if you have a lot of high resolution mods. The game just wasn't made to handle a huge amount of load.

A post of your specs would help us know better about the situation

thanks for the reply, guys.

My computer spec is

I5-4690
NVIDIA geforce gtx 1060 6gb
16gb ram

and yes, I'm using many mods including high resolution texture mod like nmc pack.

If all of my esps disabled, memory problem gone, no infinite loading, no ctd.

I just decided disable some my texture mod. thanks again. and sry for my english.

Well it's doesn't seem like it's a pc specs problem, your rig is certainly beefy enough.

Seeing how it goes away when you remove the mods, it could be a few mods conflicting with each other or you have to many? The more assets there are to load the longer it takes. Have you used LOOT? If not download that and run it. Should show you any conflicts and you can also clean your esp's with another program. Btw @panstone how many plugins did you have active when you were having the problems?

http://www.nexusmods.com/newvegas/mods/62552/? Get that downloaded son, and see how it goes

Also make sure you aren't using an incompatible driver, if you are 

http://www.nexusmods.com/newvegas/mods/53635/?tab=1&navtag=http%3A%2F%2Fwww.nexusmods.com%2Fnewvegas%2Fajax%2Fmoddescription%2F%3Fid%3D53635%26preview%3D&pUp=1

get that down you

Out of memory is the worst. Constantly plagues my TTW experience

Here is my load order.

[X] FalloutNV.esm
[X] DeadMoney.esm
[X] LonesomeRoad.esm
[X] GunRunnersArsenal.esm
[X] OldWorldBlues.esm
[X] TribalPack.esm
[X] HonestHearts.esm
[X] CaravanPack.esm
[X] ClassicPack.esm
[X] MercenaryPack.esm
[X] Project Nevada - Core.esm
[X] Project Nevada - Cyberware.esp
[X] Project Nevada - Equipment.esm
[X] Project Nevada - Rebalance.esp
[X] More Perks.esm
[X] More Traits.esm
[X] NevadaSkies.esm
[X] AWorldOfPain(Preview).esm
[X] AWOPDeadMoney.esm
[X] Military NV Backpacks.esm
[X] CFWNV.esm
[X] ELECTRO-CITY - CompletedWorkorders.esm
[X] ELECTRO-CITY - Highways and Byways.esm
[X] NVInteriors_Core.esm
[X] Interior Lighting Overhaul - Core.esm
[X] Interior Lighting Overhaul - L38PS.esm
[X] rePopulated Wasteland.esm
[X] WARZONES - Misanthropy Pure.esm
[X] NVR-Strip.esm
[X] The New Bison Steve Hotel.esm
[X] Momod.esm
[X] oHUD.esm
[X] Weapons.of.the.New.Millenia.esm
[X] AnimationProject.esm
[X] FCOMaster.esm
[X] New Vegas Redesigned 3.esm
[X] Bitter Springs Redesigned.esp
[X] Casa Madrid Redesigned.esp
[X] Gomorrah Redesigned v2.esp
[X] The Mod Configuration Menu.esp
[X] Mission Mojave - Ultimate Edition.esp
[X] jsawyer.esp
[X] Vurt's WFO.esp
[X] Fellout.esp
[X] ProjectRealityMkIv5HDR.esp
[X] Faster Start Menu.esp
[X] FalloutNV_lang.esp
[X] boa ncrpahelmet.esp
[X] Boacombat2glove.esp
[X] DYNAVISION 3.esp
[X] More Perks Update.esp
[X] More Traits Update.esp
[X] Mossberg590.esp
[X] NevadaSkies - Ultimate DLC Edition.esp
[X] No Scope Wobble.esp
[X] UnlimitedCompanions.esp
[X] AllCompanionsEssential 2.0b.esp
[X] Animated Prostitution.esp
[X] AWOPDeadMoneyVendorPatch.esp
[X] 1nivVSLArmors.esp
[X] 1nivPNSLPatch.esp
[X] BrotherhoodReforged.esp
[X] Military NV Backpacks - BumBagUseSlot1.esp
[X] Military NV Backpacks - Vendor Script Replenish.esp
[X] Military NV Backpacks - No Straps.esp
[X] Military NV Backpacks - Weapons.esp
[X] CNR_Beta.esp
[X] CAGE 1.9.3.2.esp
[X] CASM with MCM.esp
[X] Centered 3rd Person Camera.esp
[X] CFW-DLC.esp
[X] JustAnArmorPack_WithCheatBox.esp
[X] JustAnArmorPack_NV.esp
[X] JustAnArmorPack_WithCheatBoxAndAliceArmors.esp
[X] DragonskinTacticalOutfit.esp
[X] DragonskinNCRPersonnelWearingOutfits.esp
[X] DragonskinBonusPack.esp
[X] dD - Enhanced Blood Main NV.esp
[X] dD-More Gore.esp
[X] EVE FNV - ALL DLC.esp
[X] RespawnerImprovedEx.esp
[X] Respawn6Hours.esp
[X] IMPACT.esp
[X] Improved Sound FX - Weapon Sharing Fix.esp
[X] WeaponModsExpanded.esp
[X] FNV Realistic Wasteland Lighting - All DLC.esp
[X] Real Recoil.esp
[X] RWL - Brighter Nights.esp
[X] Improved Sound FX.esp
[X] Improved Sound FX - Project Nevada.esp
[X] ILO - A World of Pain.esp
[X] ILO - Nevada Skies Patch.esp
[X] ILO - Project Reality Patch.esp
[X] Interior Lighting Overhaul - Ultimate Edition.esp
[X] populatedcasino.esp
[X] PerkEveryLevel.esp
[X] zzjayHairsFNV.esp
[X] MiscItemIconsNV.esp
[X] T60.esp
[X] TGsArmorCollectionVegas.esp
[X] RWD-NV v1.4 [Standard Version].esp
[X] PipBoyLight.esp
[X] NVR-NPCs.esp
[X] NVR-Version_10.esp
[X] AWOP-MoMod.esp
[X] Portable Tent.esp
[X] WeightlessAmmo.esp
[X] WET.esp
[X] MMUE-CP-AWOP.esp
[X] MMUE-CP-Electrocity.esp
[X] MMUE-CP-EVE.esp
[X] MMUE-CP-ILO.esp
[X] The Weapon Mod Menu.esp
[X] Readius_NV.esp
[X] FlashlightNVSE.esp
[X] Weapons.of.the.New.Millenia.Cheat.Cabinet.esp
[X] Weapons.of.the.New.Millenia.Honest.Hearts.Grunt.Patch.esp
[X] Weapons.of.the.New.Millenia.Leveled.Lists.esp
[X] bzArmour.esp
[X] bzBodySuits.esp
[X] BF4_Assault_Pack_FNV.esp
[X] Reload Sounds.esp
[X] JoOsModernNCRrangersCivil.esp
[X] JoOsModernNCRrangersCombat.esp
[X] JoOsModernNCRrangersPATROL.esp
[X] JoOsModernNCRrangerweapons.esp
[X] JoOsModernNCRtrooper.esp
[X] JoOsArmory.esp
[X] MMUE-CP-NVR3.esp
[X] New Vegas Redesigned 3.esp
[X] NukaCola-Ojo.esp

and nexus mod manager showed me that i'm using 136 mods.

yeah. it is quite too much, and i didn't sort my load order.

But I remember this memory problem occured since I sorted my load order by LOOT.

So I reinstalled my game, mods, but i'm having 'out of memory' issues again, so I release this topic.

I have 4gb patcher, and NVAC, NV Stutter remover too.

I just removed some texture pack, and disabled some weather changing, visual changing esp, and seems like the problem is gone.

thanks for the all your replies, guys

EDIT : I thought my memory problem is gone, But it was not.

I just checked my FNV memory usage through task manager.

It just stay at  1000~1500Mb, at start of the game(not start menu, loading save is done.)

after 30 minutes (changing cell, using some fast travel, adventuring some dungeon, going into interior, exterior) FNV memory usage goes up to almost 3000~3300Mb.

At that situation If I change cell I get infinite loading, and ctd, and out of memory message.

I realised that Project Reality options(Subtle depth of field)make memory leaking so I turned off that option and gave me some 4~5 fps.

I thought it was some corrupted save so I restarted the game but after 20~30 minutes I get same problem.

It is really annoying, memory leaking was the real problem.

Should I remove all my mods...?

@panstone

Well I would suggest working through your load order, turning plugins off in chunks. 5-10 at a time. Turn some off, load up the game, test it out. If the problem persists, keep turning more off. Keep doing that till it gets stable. That will hopefully help you narrow it down to maybe a specific mod or mods that are causing issues.

That's the method I use whenever I had issues with Fallout 3 or New Vegas, although I never managed to do a full moddded FNV game because I had pretty much the same issues you're having, and gave up. You can also remove mods that are more so fluff and don't fully improve the quality of life in the game.

So another solution that I found might be inputting the command PCB into console commands by pressing the ~ key. It means Purge Cell Buffer, which helps with memory usage after playing a long time. Maybe this would work too?

I should probably ask if you have ever modified your .ini files in any way. There are lines in there that pertain to memory allocated to the game and exterior/interior cell buffers. Also, are you using any ENBs?

Another thing I can suggest is you pay attention to the mod WARZONES when doing your troubleshooting. I've used that mod in the past and depending on the settings, it can be very intense on the game.

Like stoobybacks said, PCB can help too. As long as you aren't using mods like Willow. In those cases it can break scripts associated with quests for that mod and possibly a few others.

Ultimately, this game runs on a 32bit engine, so even with a high end system it will never make proper use of all the resources your PC has to offer. This is very prevalent with skyrim and it's handicap that limits it to 4gb of VRAM.

A few advices to prevent "out of memory" errors and improve performance:

1/ In the Data folder "right click->New->Folder", then name it "NVSE" (I assume you use it). Only do this if the folder DOES NOT exist. Open up the Data/NVSE folder and "right click->New->Text Document", then name the file "nvse_config.ini". Open nvse_config.ini and add the following:
[Memory]
DefaultHeapInitialAllocMB=400
scrapheapsizeMB=128
Save and close.

2/ If you have New Vegas Stutter Remover, make sure that "bReplaceHeap" is disabled. Unfortunately it often causes errors.

3/ You can also install Zan AutoPurge Crash Protector - New Vegas Edition by ZanGS and Luke Gevaerts. It may contribute to make your game more stable. Don't forget to read the description.