I've got some interesting info that might help track this down. Seems that the usual "sh: y: unknown operand" when seen at the boot splash can be changed to read:
sh: sdb: unknown operand
That change from y: to sdb: seems to be caused by putting anything after copy2ram in the append line. I put fsck right after copy2ram just in case I crash, and saw this pop up.
Not a showstopper - seems cosmetic.
Copy2ram unknown operand revisited!
Copy2ram unknown operand revisited!
That's a UNIX book - cool. -Garth