Obscure errors in dmsg, system instability

[Eirik Oeverby]

Hi all,

for some time I have been experiencing weird hangs on one of my servers. 
When it happens, I can still ping it, but I cannot make any connections 
or type anything on existing ssh connections. Serial console is also 
dead, however I can enter the kernel debugger and call cpu_reset() to 
reboot. Upon reboot all is fine again.

Now I discover that my dmsg output contains a few of these:

ahc0: PCI error Interrupt at seqaddr = 0x9
ahc0: Data Parity Error Detected during address or write data phase

and

ahc0: PCI error Interrupt at seqaddr = 0x8
ahc0: Data Parity Error Detected during address or write data phase

Thing is - there's nothing connected to the Adaptec. It is enabled, but 
not used.

Can someone in-the-know tell me what exactly these errors mean, and what 
they might indicate? Ofcourse this MIGHT be the cause of my problems, 
but I don't know that for sure, and I'd like to know if there are any 
other plausible explanations for these errors...

I will obviously disable the onboard adaptec at the earliest 
convenience. This is an ASUS P2B-DS board, dual p3 with onboard u2w scsi.

Anyone?

Thanks,
/Eirik