This sounds a lot like a device is getting into an invalid state, and ***
the system's buss. I've seen this hung so bad the processor couldn't
even access the buss, since the card was *** it (an older UPA
system like an Ultra60, where graphics cards sat on the processor buss).
This could be something like a graphics card, or some other devic(It's likely doing a DMA trransfer, and getting stuck, and *** everything.
I'd switch your console to the serial port, as someone else mentioned.
If things really get messed up, it can often print to the serial port,
when it can't talk to a graphics card. This is especially true if
the problem IS the graphics card.
Also, you might notice which slots cards are in. Sometimes this matters.
All the SB1500 PCI slots are not on the same PCI buss.
Some do power management slightly different, too.
(disabling PM, mentioned below, is also a good thing)
>> Did you turn on the power management/sleep mode? If so, turn
>>that off, see if it resolves your problem. This is just a guess, but I
>>remember using it on a few desktops and they would "sleep" but never
>>come out of it correctly. You said the OS is unpatched so whatever bug
>>caused that is probably not resolved on these.