Try to swap & test the whole pair of CIAs. Last year, I fried one CIA and had the chip replaced. Machine booted, but after few mouse clicks it frozed. I tried disconnecting various peripheralls, but nothing worked out. Problem was solved when I looked more carefully into both chip designations. It seems that there are 2 major types of CIA working at different clocks (1 & 2Mhz). When I set a same type pair nodes problem was gone.
