Phoenix Gold Phorum

I installed a stereo for a friend the last few weeks I was in town before moving to phoenix WAAAAAAAY back in 2001. He has taken good care of the truck and the stereo and I am pretty proud to say its still rocking today, although I am replacing a tweeter that is blown now. It was a fairly simple system with a line driver and only 2 channels of rca's going back to a zx400 that powers a ID165 6.5" comp set. The cr/oss over is set to high pass and we used the through output then to go to a bass cube and then to the other zx400 powering a single ID10. I noticed that with a slight adjustment of the first 400's cross over or gain that the signal suddenly turns to straight loud bass/feedback noise. Any idea on what could be going out to cause this? It all still plays as normal till it touched and then its so loud I am afraid its going to blow something and can't turn it down fast enough. Any help

With the system off, take that pot that's causing that and turn it clock to clock about 20 times. Those pots get dirty.