Ok, I just had this happen today with Veronica, Completed her quest thing and she froze up. I thought it was the power armor I had just put on her but when I took it off she still wouldn't follow me. IDK what happened to her but I think this may be what happened to you. Just go back to the last place you knew where he was and look for him... he should be stupidly standing right where you quicktraveled from...
Also I have 360 version, I just took everything off of her and said "go away". I'll go back later today and see if that fixes her. I also had ED-E following me around but he was fine.
I will try that when I get off of work to see if that fixes it. Wierd thing was, I had given him things to wear and weapons to use and he used them fine for awhile. Then, as soon soon as I quick traveled after I completed the quest, he was gone. I will go back to the control pad and see if he is there. I will post and let ya know how it goes later tonight (I am PST btw)