boot loader bug???

[Stephen Sanders]

This may be a bad list to post to for this problem but I'm having an
issue where in it appears that the boot loader fails and then overwrites
the MBR with 0.

The system boots to :

F1 - Linux
F3 - FreeBSD
F5 - Drive 1"

Default:

But then fails on "boot error".  Rebooting will not even make it to the
prompt above and if one checks the MBR (via a PXE boot), it has been set
to 512 bytes of 0.

Sound familiar?  Thanks