Yesterday, when I had to restore some data for the user it failed. I was sure that I have all the necessary tapes. When I checked library I noticed that one of the tapes has suspect status.
After short searching for a solution, I found out that I have to change status in SQL.
osql -E -S DB_Server_Name -d DPM_DB_NAME -Q "UPDATE tbl_MM_ArchiveMedia SET IsSuspect = 0"
You can run this command from the DB server or DPM. It will change all affected records.