Are you positive GRUB is being written to the MBR of the disk you're set to boot from? I'd double-check your BIOS settings just to be sure. Since you mention it, you could boot from an Ubuntu cd and run grub-install (http://www.gnu.org/software/grub/manual/html_node/Invoking-grub-install.html). Presumably if this fails you will be able to see why. -Brian