First I am far from an exoert but here are somethings you may try
At the grub menu type c, which will take you command prompt.
I think will show you the root for your pcbsd as seen by grub.
You can also do grub>
and it will let you know if it in deed is a bsd partition.
Also I think if you do dmesg in console you may find some useful info in the output, don't know all the commands so just dmesg may give you LOTS of stuff.
Hope some of this help :idea: