I have an A4000T and have seen this problem as well as the purple screen.
First I would try re-seating the daughterboard module for the CPU.
Then - if you have a Cyberstorm installed, re-seat any memory SIMMS -maybe try booting with only one SIMM at a time.
Make sure that the plastic legs under the CPU module go through the holes in the board., There should be a satisying "thunk" when you re-seat the CPU module.
Check or remove any slow motherboard memory - re-seat them.
Good Luck.
