The NCR will attack me no matter what my reputation with them (I am currently "liked"). The only way I have found to get around it is to wear NCR clothing 24/7 but I still get attacked by NCR MP's at times.
Is there a way to fix this? (FYI I have searched the web and found that I am not the only one with this problem)

I have the same problem, but only when I enter their building in their camp which is located near New Vegas. So one load and don′t go there and it is OK:))

faction armor maybe? if ncr see you with bos or legion armor they will attack atleast they did when i had bos power armor on

its not faction armor. the only faction armor I have in my invintory is NCR Ranger Armor

your going to have to do low level quests with ncr
the kind that get issued by lower ranks (who cannot see thru your disguise)

most of the people in fort mccaran will talk to you and have quests
this should raise your rep

im not sure if vault 22 quest counts because the leader isint true ncr

also would have helped if someone told me the TOPS casino is NCR before I killed all the chairman..

edit
just rememebered, you might gain standing with NCR by killing Legion members
much like how when you kill powder gangers you gain rep with goodsprings

also, try equipping a high level NCR armor, like the masked armor, or power armor
this might make it harder to detect you

good luck

I had a good NCR Rep so I don't know why they are attacking me.

Oh if it means anything I've had the NCR Rangers hunt me down and try to kill me.