I have the same problem after updating the bios to version 1520 (from 1517)
I found a solution. Move your PCIe card to the second slot. It works (the BIOS update made the first PCIe slot dead).
My system was updated from version 0027 to 0028 (I was trying to troubleshoot the audio problems with the display).
I am using the SIIG SATA II PCIe RAID adapter. I have the DH55HD board with a 2.8 GHz Clarkdale chip.
I did place the card in the second slot and it worked. What I discovered, however,
is that is stopped working again when I changed the BIOS setting back to ACHI as
controling. The raid card works if you just leave the BIOS set to Onboard.
The BIOS seeting needs to boot to ONBOARD and not ACHI.
I solved this by following John directions and moved the card to
slot #2. However, I lost the RAID as soon as I switched the BIOS
to boot from ACHI again. I found that either slot will work as long
as the ACHI to boot BIOS setting is not used.