I suggest rebooting after clearing and stopping service.
I have two xoomys and after attempting this at least 10 times, I decided to reboot after completing the second step.
After unlocking I went straight to update now and there it was waiting for me!
I started the download on that one and picked up my wifeys xoom.
On wifes xoom I cleared and stopped service.
rebooted.
unlocked
checked for update, not there
cleared and stopped service
went back to check and there it was waiting!
Thanks for the heads-up!