8GB CF card doesn't boot with grub in LBA mode

8GB CF card doesn't boot with grub in LBA mode

We have an existing embedded Linux system that uses 4GB compact flash
cards. We have now been given 8GB CF cards to try. Using dd to duplicate
the 4GB image onto 8GB cards, then lvextending to use the new area of the
card.
When LBA mode is turned on, it boots to a GRUB (0.97) command line, but no
variations of commands seem to make the drive boot properly.
When LBA mode is turned off in the BIOS, it boots into Linux correctly and
everything is ok. Unfortunately, as this is an embedded system, we can't
go changing the BIOS for all the systems out there (no screens or
keyboards!).
The partitions are set up correctly, when using non-LBA mode, the drive
boots, and the partitions report correctly (including the extra 4GB).
Any ideas?