grub goes into "rescue mode" after renaming 'default' boot environment

[Kostas Oikonomou]

Before upgrading from 9.2 to 10.0, I created a new boot environment
named 'pcbsd10.0'
with beadm.  Then I activated it, and renamed the 'default' environment
to 'pcbsd9.2'.
As a test of the backup BE, I deactivated 'pcbsd10.0', reactivated
'pcbsd9.2', and re-booted.  

The machine failed to boot, and grub went into rescue mode:

GRUB loading.
Welcome to GRUB!

error: file 'default' not found.
Entering rescue mode...
grub rescue>

Apparently, it is still trying to find a BE named 'default'.   I finally
booted up by doing

grub rescue> prefix=(hd0,msdos1)/ROOT/pcbsd10.0/@/boot/grub
grub rescue> insmod normal
grub rescue> normal

But this problem recurs every time I reboot, either into pcbsd10.0 or
pcbsd9.2.


                                    Kostas