You wanted to change your Media ID Generation rules after adding your Tape Cartridges, and after re-inventorying your tapes, you started facing an error like the following:

incorrect media found in drive index 0, expected FSD300, found D300L4, FREEZING FSD300

Reference : http://seer.entsupport.symantec.com/docs/276993.htm

Try to re-label your tapes, using the GUI or the bplabel command.