System lockups

Having a terrible time finding a solution to this problem…….AMD450 box had problems locking up with no direct indicators…no particular program just whenever it felt like it…the only thing I noticed is when using scroll function on mouse seemed to be happening more often….ended up replacing the enire system hardware/software…still same problem….I have narrowed it to the extension cable on the keyboard or the phone line?? any direction on this greatly appreciated…need more info email me corey@bridgenet.cc