I tried using the IP address in place of the computer name in the user defined selections. I am still getting the same error as before.
For what it's worth: Over the weekend, my daily differential backups failed. It appears that Backup Exec attempted to backup the remote share even though it was not selected. The error message for the remote share was:
a000fe39 - Authentication failed on connection to server
I noticed that even though the remote share is not selected under "Selections", it is still listed under "Resource Order" and "Resource Credentials".
I couldn't figure out how to delete the remote share from these lists, so I made a new differential backup that only includes the drives on the server. I won't be running this backup until Tuesday night, so I can't say if it works properly until Wednesday (bear in mind that the old differential backup passed the test run OK but failed during the real backup).