that error shows on re-install of grub....you put the bootloader link files to the external
just redo grub in mbr to re-link to the internal ones.
a live cd is best
root (hd0,0)....read my signature if linux /boot is not first partition
2) if you have no live cd...suse should have a recovery mode or rescue mode where you can re-install the bootloader...hopefully with an option to go to internal drive but maybe not....in which see if it has an option to go to console mode...then try above commands
if you do not understand grubspeak after reading my sig tell us your internal drive partitions pls