Problem with Musical Fidelity A3cr pre-amp

Has anyone had this problem?

I have a 3.5 year old A3cr preamp that distorts on loud transients in high frequencies and on sustained pure high frequency sounds. I tried everything else and I'm pretty sure its the pre-amp. It depends on volume and frequency make-up of source, but it is quite annoying. It is not equally bad on all inputs, but it is there.

I use the pre-amp with an A3cr amp, analysis plus cables and Magnepan 1.5Qr's. I tried different inputs, cables, amp and speakers, the problem really seems to be the pre-amp. I originally thought it was the speakers since it sounds a little like a torn cone on a paper tweeter, but it is the pre-amp.

Does this sound like anything you've heard of? What can be done? I live in the Boston area, but I have the original boxes if I need to ship it. Does anyone have any idea of cost for repairs?

Thanks