I was doing a simple mission at Camp McCarran, (not to far into the game) Im not sure if I was one "I put a spell on you" or the one where I ask around for the General Hsu (or whatever his rank is), any ways I had gone upstairs above Hsu's office and there were two guards next to a door, I didnt even get close to them before they started chasing me and shooting... now I cant even enter the dang camp without having half (and only half, not everyone there tries to kill me. I swear I did not steal anything or even have a weapon on hand, I didnt want to decide weather I was agaist or with the NCR so I have made sure not to do anyhting against them... yet.. Any ideas how I could finish the mission with out being killed or why Im a target now at all?!

Were you wearing anything from another faction?

I don't know the layout of Camp McCarran that well, but I'm guessing you walked into the "danger zone" for the monorail. The guards (and everyone else) will become hostile if you go past that point. The same thing happens at the LVB Station on The Strip, if you go past the door at the back of the building where the two guards are standing watch.

That's what it is. The NCR don't let you into the monorail by default, they have to like you.

In a couple of NCR bases there are doors with Red Lights that you don't want to approach or you will get shot. At some point, depending on what you are doing, you can go through those doors.

Now, they do Warn you as you approach, if you hear it in time.

The problem is, when you are set to Always Run, you are on top of the gaurds before they can warn you to stay away. I had to reload and Walk up to the area to get the warning.