So, I had ED-E as my companion since I fixed him up in Primm. Then when I got to Freeside I also picked up Arcade (yes, I had both of them as companions, which I'm guessing is another glitch). Since I didn't want Arcade around, but wanted his bonus, I told him to wait where I found him. AND since I was getting pretty pissed off about the music ED-E kept blasting in my ear every time I got into a fight, I told ED-E to wait at the Mormon Fort as well.
So, time passes and I'm doing the Beef mission at the Ultra Lux. I'm dressed up as a White Glove, and I have to wait for about 13 hours. When I get out of waiting, I'm told that ED-E and Arcade are no longer my companions, and both have been sent back to where I found them.
I go to Primm, into the Nash shop, and find ED-E and Nash in a shoot-out, and ED-E is red on my radar.
Arcade is fine, I picked him back up and sent him to the 38, so the problem is only with ED-E. Maybe Nash just doesn't like robots?

This happened to me as well, it was so frustrating.. i mean why the hell does he go bad/evil/angry? I R MAD