I've been working close with the NCR for quite some time in my current play through. I've managed to get to Vegas (after getting EVERY map point I can find) and start doing jobs at the NCR Ambassador's request. Just after I get back from finishing the mission for The King to stop attacking NCR, I drop off the quest, and an NCR MP comes up to me, accuses me of screwing with the NCR, and attacks, and not just him, but every NCR who is around joins the fight.

As far as I know, I've been perfectly loyal to these guys from the start, I have an Idolized reputation with them, I'm not wearing any enemy armor (Just some black armor I took off the Vann Graff thugs *shuffles the bodies in a corner*), I have NEVER attacked an NCR member or killed one. This doesn't make sense, has this happened to anyone else?

Try not wearing the Vann Graffs armor. Though that shouldn't be an issue cause its what I wear and they don't attack me.

Wasn't the Vann Gaff, they still came at me and beat me like a bad puppy.

Have you ever wore an enemy armour? Such as Caeser's Legion or Powder Gang?

As I said before, no Ceasar Legionare armor, no Fiends gear, nothing on that would rile them up.

I managed to run out of town and leave the area, came back, and the guards liked me again. Not sure what started that mess.