I have a feeling this has something to do with mods. Anyone know a way to fix this?

Are you wearing NCR or Powder ganger armor?

No, and I tried taking off all of my armor and entering town just in case I'd repaired my armor with faction armor, but it didn't change anything. I think it has something to do with http://planetfallout.gamespy.com/mods/515/The-NCR I deleted the .esp from my load order and my directory, but I'm still having the problem... Do you know if I'm fully uninstalling it? Because there's no uninstallation directions in the read-me or the description.

Edit: Yeah, it's definitely that mod. I loaded a save from before I joined the NCR in the mod, and they didn't attack me.

Someone help me out here. I can't play New Vegas until this is solved.

Try using the removefaction command as follows:

player.removefaction [faction]

for the [faction] part of the above command, use the NCRs faction ID of 000A46E7 --> player.removefaction 000A46E7

Alternatively, if that doesn't work try the removefromallfactions command. That should certainly do it, but as should be clear from the syntax of the command it removes you from ALL factions in the game. If you're just now getting to Nipton this shouldn't be a problem as most of the important factions should still be neutral or not even know of you but be aware of it if you try that command.

Anyways, hope this helps.

Nothing's working. Oh well, I'll just start a new game.