Hi Mary,
Does the original server require Backup Exec anymore?
If not stop and disable all the Backup Exec services except for the remote agent.
Then push out the remote agent from the 11d server to the "9.1" server. It will upgrade the agent to the latest level.
Then you should be able to back up the "9.1" server from the 11d server.
bear in mind that the jobs would be set up on the 11d server and backup exec would no longer run on the 9.1 server.
Thats what I would do anyway.
Good luck
Gilly