So I'm looking at my status and I'm currently Idolized by the NCR. However, when I put on any NCR armor, my NCR fame suddenly disappears from the status... and all NCR locations are back to Neutral, as if I never met them.
Why is that?

This has happened before and after the patch.

Because it's faction armor. When you put it on, you are actually donning a disguise. It should all revert when you take it off. WARNING: wearing that armor around guards or officers will make the them angry and start shooting at you. I have no idea if that's permanent.

So basically, you never officially become part of the NCR? Just a phony in disguise?

i think its permanat or a bug or something because even if im not wearing the armor guards still spot me and i should have Accepted reputation also when i do wear some armor i get spotted if i kill person who spotted me nothing else happens i get no reputation hit and no one else attacks me. i cant even go to the embassy because every time i get near the MP go hostile and start attacking so i cant turn in quest to clear my bad rep.....i think im going to start a new char and screw around with mods till they fix this game that i love so much T_T