Does Trisquel boot correctly, from the hard drive you installed it on? Did you have to chroot into it and grub-install to get it to work? Did you install off a USB (in my experience that always messes things up- every USB install has me chrooting in with a live CD and setting up GRUB manually).
Few extra bits of information- can you describe your bootup process to us? Can you show us the contents of /etc/default/grub and /boot/grub/grub.cfg? Your situation is indeed mystifying.
