Hi Vince,
I had a similar problem and found out, that I forgot to execute FUSER command.
After killing the stale SQL*Plus sessions, I re-ran the mopatch and it finished successfully:-)
Quote from SBP installation guide:
"After having shut down all database processes as described in the previous step, use the fuser OS command to check for stale SQL*Plus sessions:
$SBPFUSER $IHRDBMS/bin/oracle
If that command reports running processes, these are stale SQL*Plus sessions, which you can safely terminate with the kill command."
Lucie