ahc0: Data Parity Error Detected during address or write data phase

[Benny Helms]

3 days ago, my VA Linux server running FreeBSD 4.4-RELEASE began filling my
logs with the following messages:

 ahc0: Data Parity Error Detected during address or write data phase
 ahc1: PCI error Interrupt at seqaddr = 0x9
 ahc1: Data Parity Error Detected during address or write data phase
 ahc1: PCI error Interrupt at seqaddr = 0x9

A google search shows a lot of questions, but no real answers.  At one
point, during a reboot, one of the three SCSI drives that are RAID-5 showed
a red light, which went away after shutting the server back down, taking
canned air to any dust in the machine (including pulling out the hard
drives, blowing out their slots, and reseating them).  Because of that red
light, I decided to put my spare drive into play where the suspect drive
had resided.  Took over an hour for the raid software to rebuild the new
drive, and when it rebooted, the error messages resumed immediately.

Does anybody know what this error is indicating?  I'd really like to fix
this.

Thanks!

Xitron