The errors:
[90:190] Invalid format version of Data Protector medium.
[61:17112] Medium header verification failed on drive
are very well-known. They mainly seem to occur on Tape drives that are accessable by Windows systems, and based on this "Changer0:1:0:0 ", I am thinking that this is a Windows system
The cause of this problem is having a service named "Removable Storage Manager" (RSM) running. One of the things that this service does is to poll all the SCSI-attached storage devices with a Tape-Unit Ready signal. If a drive is doing a backup at the time it receives this message, it is interpreted as a Rewind signal, and tries to rewind while the tape is being written to, corrupting the header file on that tape
When the tape is getting ready to eject, it is re-wound, and the header file is read. If the header file is corrupt, you will get these messages, and the tape is unusable until it is re-formatted. Needless to say, anny data written to the tape is gone
Each Windows-based server that has visibility to your tape drives must be manually examined to see if the RSM service is running. (You can check visibility by going into Device Manager, if you see Tape Drives or media Changer, then the server sees the tape device). If you find a RSM service running, it must be stopped, and disabled, so that it can't restart when the system is rebooted
It needs to be emphasized, the problematic server does NOT have to be in the Data Protector cell, simply having visibility to the tape drives will make it a candidate to cause thei problem.
The SAN administrator (if in a SAN) should be able to see what machines are zoned to be able to see the tape library