I have a Dell PowerEdge 2650 with on-board Adaptec Perc3Di SCSI RAID ontroller (mirrored 18GB drives for OS). It also has an add-in Adaptec 2810SA 8-channel SATA RAID card. After installing FC3, and installing GRUB to the MBR of the mirrored 18GB drives for OS, when I boot the system, I get "GRUB Loading Stage2Read Error".

The Dell system and both RAID controllers were updated to their latest BIOS versions prior to installing the OS.

I even tried (to no avail) booting into rescue mode, chrooting, and running:
"grub-install /dev/sda".

When I remove the add-in card from the system, grub works perfectly off of the on-board Adaptec Perc3Di SCSI RAID controller (mirrored 18GB drives for OS).

I don't think the latest Dell BIOS for this machine has the provision to boot from add-in cards first, or to prioritize add-in cards after the on-board devices.

I do know that the SATA add-in controller definately comes up first after POST before the on-board SCSI controller's BIOS.

As suggested by various people, I booted the system into rescue mode using the install cd. Once booted, I chroot'ed, then ran:

grub
grub> root(hd0,0)
grub> setup(hd0)

This command did not return any errors. All output looked successful and normal from my experience on single-disk systems.

/boot/grub/devices.map, fdisk -l, and grub tab expansion output all confirm that /dev/sda is indeed (hd0), and root is definately (hd0,0).

By the way, I also verified that /dev/sda1 is bootable, and that /dev/sdb1 is not bootable.

Now, when I boot the system, instead of getting a grub stage 2 error, I get a grub stage 1.5 error.

Any help would be greatly appreciated.

Didn't the GRUB manual link I gave you over at fedoraforum.org help you with that 1.5 error message you got?

Unfortunately, no. Thanks for the link anyway.