GRUB errors - despite clean new install

I have been trying for the past few days to install Ubuntu (both Hardy and Intrepid) on my AAO110L as a command-line base only minimal install. To this end I have used the minimal install ISO as well as the alternative install ISO for both versions. These were not burned to CD, but transferred to USB key (via Unetbootin on a Windows Vista machine).

The install over broadband (nothing seems to be loaded from disk) goes fine, but no matter what Ubuntu version or installation approach I've used, I get the same error after booting GRUB:
Error 21: Disk does not exist
I've tried fixing GRUB with the supergrub live-CD, but to no avail. When using supergrub to boot directly off the primary partition I get an Error 13...

I only have 2 partitions, an ext2 partition (have tried ext3 as well just in case) flagged as bootable and a 0.5GB swap partition. I've even reformatted the hard drive and deleted GRUB from the MBR using supergrub before attempting another install, but the same problem.

It doesn't look like anyone else has these issues... Can anyone help???? Thanks!!!!