I was just following the standard quest line (I only just arrived at Boulder City), and I've been doing everything the NCR would like: I restarted Helios One, though I evenly distributed power a cross the lands; BUT I didn't kill a single guard dog, nor did anyone see me near the guard dogs, while operating the exterior terminals.

I got them control of Primm, I cleared out their valley of critters near the Mojave outpost... I haven't stolen a single thing nor have I shot any of them.

During Boulder City, I shot dead all of the Great Khans and successfully rescued the hostages.

The only thing I could POSSIBLY have done that they wouldn't like is I let Layla go when she tried to rob me at the Primm casino. Except, that happened before the last time they were all friendly with me. I did rescue the powder ganger hostages, but that shouldn't matter since I then went to the prison and used it as a targeting range.

The dividing point was when I had a companion (Boone) dressed up in NCR armor, and then I stripped him of his armor and told him to go back home so I could add Veronica to my party.

Also, not all NCR hate me. Only CERTAIN ones: Like Private Kowalski at Boulder City. None of the other NCR there dislike me, I can talk to them so long as I'm out of his aggro range; if he sees me though, he will attack me on sight and they will join in.

Same with the NCR arms merchant and a destitute traveler at Veronica's trade post place: they HATE me, everyone else only follows suit once they notice me.

I have noticed that if I mod things so that Private Kowalski's AI data is set to 'Unaggressive' instead of it's standard 'Aggressive', he no longer attacks me on sight and acts normal.

And for the record: though I've been trying to be friendly, I'm still technically neutral with the NCR _BUT_ if I raise their reputation through the console they still will hate me, it makes no difference. And I'm enemies with the powder gangers and the legion, and friendly with the various towns I've been to.

I've also tried adjusting my Karma to be maximum, that doesn't fix it either.

The only solution I have been able to muster is wearing an NCR uniform--then, nobody attacks me. Except, what the Hell? Why does that work but raising their reputation manually doesn't?

Also, I tried querying in the console if I was set as the enemy of any of the factions Private Kolawski, and it said I wasn't for all of them.

---

This is pretty much game-breaking, 10 hours of gameplay (I've been taking my time exploring) down the drain, and I'm thoroughly irritated.

If someone has an idea of how to fix this, please help.

Also, for the sake of getting that very assistance: here's a link to my save game. Have at ye: http://www.mediafire.com/?cpo5c6paholszt5

And also I have some links to other pages, this is apparently not an isolated problem... this doesn't really help, since all of these pages resulted in people NOT solving the problem, but at least adding these links might increase the likelihood of it being fixed in a patch.

http://www.gamespot.com/xbox360/rpg/falloutnewvegas/show_msgs.php?topic_id=m-1-56879315&pid=959557
http://answers.yahoo.com/question/index?qid=20101024210513AAlniAL
http://www.gamefaqs.com/boards/959557-fallout-new-vegas/56906539
http://www.gamefaqs.com/boards/959557-fallout-new-vegas/56882086
http://www.gamefaqs.com/boards/959557-fallout-new-vegas/56879315/629037777
http://www.nma-fallout.com/forum/viewtopic.php?t=51118&sid=ad595d59177f95254f5bb55847f9714d
http://www.gamefaqs.com/boards/959557-fallout-new-vegas/56832109/628581805

Just wanted to let you know.. I've stopped playing until the comprehensive patch comes out. I'm neutral with NCR, but they attack me on site unless I wear NCR armor, then only the unique NPC's will attack me (so it still is a problem). I'm also vilified with Caesar Legion, but they show up friendly to me. I've actually annihilated an entire Caesar camp because they refused to shoot back.. I don't get it.

From http://fallout.wikia.com/wiki/Boulder_City:
On entrance, there is an NCR memorial to soldiers who died at the Battle for Hoover Dam, being looked at by Private Kowalski, if the player shoots the memorial Kowalski will draw his gun and if shot a second time he will attack.
Perhaps you shot the memorial by accident? Or on purpose?

Shooting the memorial will cause Kowalski to confront and attack you. The only way to get out of it is with a speech of 30.
Try putting your gun away or draw it and put it away (this is supposed to sometimes let your enemy know you dont want to fight).
Or try putting on ncr armor and speak to him?

Also note that wearing armor from an opposing faction will get you shot at.
Did you try to steal from the merchant?
Any mods installed?