You may be able to run diagnostics to try to get information on what's going 
on. Definitely inspect OS logs and the TSM Activity Log for any details on the 
error condition. Also, verify that your drive and library firmware levels are 
at an appropriate version: replacement drives may come with an old firmware 
level, which could cause problems. Your tape drive technology may support 
TapeAlert, which could then be turned on. If still problematic, you could try 
putting suspect drives offline to try to isolate the troublemakers. An unlikely 
cause of problems would be a bad batch of tapes. (I once unspooled a name-brand 
problem tape to see if it had a physical media problem - and actually found a 
factory splice!)

    Richard Sims