I need some help, fellow players who've beaten the game. I'm at a loss (and the internet doesn't seem to help here).

After talking with Yes Man, I'm given two new quests, both state NCR (idolized) and the Legion (infamy, but I carry the mark of Caesar, and they don't attack) will hate me if I continue talking to it. Okay, since I'm favoring the NCR, I suppose that'll do for the rolling bread box.

I speak to the NCR ambassador, who requests my help relating with the Boomers. Since I'm idolized there, this should be easy, and it was. I return to the base and report back.

However, on my way out, I'm attacked by one of the guards. I take it out (thinking it's a Legion spy), then the other guard attacks. Both non-guard NPCs remain green. Okay, I wipe that pest off the earth as well. When I walk outside, I'm not only attacked by the NCR guards there, but the Securitrons help out.

Wait. Didn't the ambassador just tell me guns + NCR = forbidden by Mr. House? How do these guards carry weapons, and more importantly, why are the Securitrons attacking me? Oh, I should point out neither I nor Veronica (passive) have drawn weapons.

Of course, I'm so surprised, I'm shot dead. At this stage, I have no powerful weapons, having left them in Lucky 38 because I tired of the game's constant "We'll take those, please." I only keep my 10mm pistol on me (and Veronica has the same).

So the game restarts, only to introduce the same outcome.

What pisses me off here is the Infamy I'm gaining because of this... glitch. I can't seem to find any way out of this, so this is where you come in!

Does this occur because of the quest given after talking to the Yes Man or is it a glitch that's inherent into the game?

I can reload a previous save to bypass Yes Man (it'll svck, badly, but I'll do it) and go straight to the embassy, but if it's inherent, how do I complete it without Infamy?

Fallout wiki says Infamy will not be granted, but that's not true. I get it the second I kill the guard who's attacking me.

My concern here is the Infamy, not the quest itself. Because I've done many quests for the NCR at this point, I'm afraid if I get the Infamy, I won't have enough quests to regain the status back to Idolized.

Any help/advice will be appreciated, except those telling me to go independent or join the Legion. I'd like to stick to the NCR option, if I can.

Are you attacked by an NCR MP? Because it's a sort of bug where he attacks you regardless. What you need to do is just not attack run into the sign store across the road, he'll follow you in then just kill/sneak kill him and none of the other NCR or securitrons will attack you. Sneak attacking him (Just run round the corner and crouch) should avoid any karma loss. Hope this helps.