The PS in the A4000 desktop is meant to pull air in from the right side at the back. The air is supposed to move over the slots before reaching the cpu and then being blown out the back of the power supply.
I had a revision 3.0 Commodore cpu board with the 25mhz 040 in it originally. This cpu board revision had issues with heat. As the interior temperature would go up ( not abnormally ) the machine would get progressively slower and then lock up. I solved the problem by putting everything into an old 386 AT tower. Then I put a CSPPC 50mhz060/233mhzPPC with 128 megs ram on it. That turned out to have an issue with heat also. So, I put extra fans blowing on the ppc. I think the cpu fan for the 233ppc might not be adequate.
Anyway, first thing to look for would be heat related problems considering the accelerator you have. Also pull out expansion cards and try the machine with no cards in the slots. Some older cards don't always behave well in newer machines. An other issue might be a weak power supply.
