Whoever told you that this is a Data Protector error is right, and you were right in opening a support ticket. I doubt if you will get the answers that you seek here, mostly because DP 9 is only out about 2 weeks, and we don't have a history with it
When you Scan a media, the media gets loaded into a Drive, and the header file is read. The media is unloaded, and the IDB is updated. This is why, after you scan, everything looks to be correct
Are you able to manually format one of the tapes where you got the message
"data protector Medium in device *** cannot be initialized"
If so, then this is what needs to be pursued by the Response Center first. You may actually have 2 (or more) problms, the other involving the Internal Database, or the GUI