5.2.1-RELEASE hangs at F1 prompt

Greetings!
  I am trying to install FreeBSD 5.2.1-RELEASE on an Intel ISP2150G. This is
an L440GX+ motherboard in an Intel chassis with a SCSI backplane.

I made a bootable CD and the install seems to go fine. Upon reboot, I get
the:

FreeBSD: F1

Prompt and when I press enter, I just get a beep. Looking over the lists, I
gleaned that I needed to double check that my partition was set bootable,
and it is. The odd thing is that when I detach the SCSI backplane and hook a
68pin SCSI drive directly to the onboard SCSI controller, it installs and
boots fine. I get the same results with IDE disks. This would mean that the
backplane is suspect bad or incompatible, but I know that it works okay with
Windows 2000. To further complicate things, when I remove a drive from the
SCSI backplane and use an external 80 to 68 pin adapter (bypassing the
backplane), I get the same install okay, but no boot.

I have updated this system to the latest BIOS, BMC, FRUSDR, and HSC for the
chassis and backplane as well as gotten current firmwares for the various
Hard Drives I've tried. They are as follows:

Seagate ST39236LC    9G 80pin
Seagate ST336607LC  36G 80pin
Fujitsu MAN3367MC   36G 80pin
IBM     DDYS-T18350 18G 80pin
IBM   IC35L018WD210 18G 68pin

All but the last drive don't work in the SCSI backplane or in an 80 to 68
pin adapter. Any suggestions?
  Thanks in advance.
  -Sam Clements