Hi Brian,
Thanks for the tip. The board is overclocked (I checked the numbers on the board no scsi, 25 Mhz 040, 160 mhz ppc). It's overclocked to 33 mhz 040 and 200 mhz ppc.
I tried another memory module I had the same instability problems. The crashes are at random sometimes after boot sometimes after 15 minutes. My maximum is about 30 minutes stable.
It could be power because the overclocked CPU need more power. They don't get overheated I think (the PPC gets warm but not hot and the 040 has a big cooler and fan and stays cool).