Im posting this hoping that this is one of the bugs Bethesda is addressing but if not, I hope you read this because I cant go any further in my game until this is fixed.
First of all this is my second playthrough and the bug happened again.
After chasing Benny out of the Tops Casino, a person from Caesars Legion stops me, tell me to go meet Caesar and that all of my crimes against the Legion are fogiven. But once I get to the camp all of Caesars Legion is still hostile including Caesar himself which of coarse wont allow me to finish my game. And the same thing is happening with the NCR. I really hope that this is one of the bugs that youre fixing because I can deal with radscorpions being stuck in the ground and npc's walking through walls but at this point I cant even play the game.
Help me Obi Wan Kenobi, youre my only hope.

Put on McCaffery's hat, lets hope you haven't turned it in yet.

http://www.gamesas.com/index.php?/topic/1123619-gomorrah-exit-crash/

I love this game too much (even with the bugs) to turn it in. What and where is McCaffery's hat and how will that help me?

The twins from the (casino in Freeside, dont remember what its called) ask you to kill this dude, and return his hat to them, he hangs out there. I was stuck in a casino until I equipped it because I couldn't go back to the strip, You can also try the mass / various steps I did to see what works.