By installing grml on a harddisk with an already existing vfat partition grml2hd
realised the existence of the partition and installed the system after
formatting it as ext3. But it didn't change the partition table, so there was no
way to boot from the freshly installed grml system. I would expect grml2hd to
change the partition id accordingly instead of leaving it as a fat partition in
the partition table.
Furthermore the bootable flag hasn't been set to the partition, so the installed
grub in the partition could not be found during the booting process (lilo would
have been found either).

Digging through the code of grml2hd in hg.grml.org I could not find any
functions assigned to these tasks.