Marc,
Open the library, remove the tapes from the tape drive manually, put the tapes you took out of the drives and stick them back into the library slots.
Close the doors
Stop all services bpps -a (all stoppped) on all Servers Master and Media? Now restart the Netbackup server and media servers.
Activity monitor clear?
Now look at the Media tree, is your restore tape in the list?
YES?
Try the restore now.
JD