Hi Fran,
I had the same kind of thing happen to me with Imuran. I tolerated it ok for a week or so, then started to develop a low grade temp, then started with back pain. The back pain got worse and worse, thought it might be kidney pain, finally went in to the doc and he wanted to do a lumbar puncture. He was thinking that the temp along with the back pain (to the point I was having trouble walking) might possibly be spinal meningitis. I asked him to talk to my nephrologist first and the first thing he did was tell him to take me off the Imuran. Within 2 days the symptoms were gone. It might be that Imuran is one of those drugs that take a little bit to develop a reaction to. I'm glad they figured it out with you too!
Lori