Yeah the New Vegas engine is pretty limited, anywhere above 139 plugins and you'll start seeing this happen. Just disable or merge any of the smaller, non conflicting plugins until you're at least down past 130, and it should stop (although the smaller you can go, the better.) I've also heard some people say that this problem continues on saves that hit the mod limit, although I've never experienced it myself. If you continue to get the bug after disabling enough plugins, then try making a new save to see if the problem persists.