5.2.1 on EPIA M1000 board

I have had an awful weekend trying to make sense of wild errors that 
FreeBSD has been throwing on my VIA EPIA M1000 board.

5.0 seemed to be going fine, until I tried to make buildworld using 
5.2.1 sources. Then it crashed and reset halfway through. The second 
attempt worked, so I built and installed a 5.2.1 kernel. Then the fun began.

5.2.1 would not accept my hard disk. Attepmting to boot normally, or 
mounting drives after booting into single-user-mode, would cause a 
stream of errors.

Thinking the crash had screwed my hard disk data structure, I did a 
fresh install of 5.2.1 from the release ISO from the FTP site. Booted 
fine on a Pentium 4 machine, but went beserk again on my EPIA board.

The error I'm getting looks like this:

ad0: FAILURE - WRITE_DMA status=11 <DSC,ERROR> error=84<ICRC,ABORTED> 
LBA=4127103

Such messages would stream up the screen, the drive crunching wildly. 
Any successful access (booting from a kernel.old 5.0 kernel, for 
instance) would complain about the filesystem being dirty, and leave the 
system read-only until fsck was run. fsck would run, but would find 
dozens of assorted errors which it could not correct.

I posted this to freebsd-questions, and someone replied with something 
along the lines of 'me too' - they say that they can run 5.2.1 on a 
Compact Flash card, but will get wild problems too if they attempt to 
boot it from any hard disk.

Also, should it be of any interest, I can only run 5.0 if I disable UDMA 
access to the Primary IDE Master in my BIOS settings. FreeBSD obligingly 
drops to PIO mode. Any ideas on this?

-- 
Bob