Loud squealing followed by a grinding sound

My husband recently changed the
main serpentine belt on my 2001
Chrysler Sebring. Now when I
drive with my AC on it makes this
very loud horrendous squealing
sound followed by and almost
grinding sound. It only does it 3-4
times when I'm running the AC
when I first start the car in the
first 5-6 minutes of driving then it
doesn't do it anymore.  My
husband is a fantastic mechanic..
He said he has never heard a
vehicle make that kind of a sound.  
Does anyone have a clue? He
checked it and made sure it was
tight and we conditioned it with
belt conditioner and it still does it.
It's really loud and embarrassing.