Sorry, this:
"...when I try to restore from Restore > Restore Sessions, the plus sign does not show anything to restore..."
implied to me that you could not see any session
I cast a pretty wide net in my research for this problem, but, all I could come up with was there was an incompatability with a Session Manager test binary. I don't see how this might affect you, unless it was caused by the Backup. On your
Cell Manager, run
cd \Program Files\Omniback\bin
bsm -ver
I also found some clues that this may be able to be overcome by exporting and re-importing the media used in this backup to get back the catalog
Now, here is where this gets sticky. Normally, I would ask for session detail and session media reports from the Backup session, but, this would be disclosing your private system information to the world
At this point, you should probably open a case have have some GUI debugs run