We had 3 policies running, they all stop writing to the tape drives at
about the same time.  No errors that I can find, nothing in the server
event logs, Veritas is looking at the NetBackup logs but I don't know if
they will find anything there.  The only way we have found to get
everything talking again is to down the server, power cycle the library
then boot up the server.  Stopping and starting the services or even
rebooting the server doesn't seem to do it.  The other media servers
don't seem to have these issues, but they are not backing up anywhere
near the data that the main server is.

We started to have this issue with our original master/media server, but
since that hardware was coming off lease we didn't chase it too hard.
It mostly happens on the weekend when we are using all 6 drives for a
really extended time.  First we have trouble with one drive, then it
spreads until nothing is moving.

All new server hardware, Clean load of Windows 2000, SP4, windows
updates applied, new HBA, talking thru a new fiber Switch.  Qualstar
412600 library, we have half of it for Windows, the Unix guys have the
other 6 drives and 300 slots.

Clean install of NetBackup, moved the catalog databases over then
upgraded to FP3, then up to FP5.

It worked pretty well for a while, then the problems reappeared.

Replaced the fiber-scsi bridge in the library so at this point the
hardware and software is all different pretty much end to end and we
have chased the drivers as far as we have been able to determine.