Are you just using Backup Exec 2010 R1? If so you should upgrade to the Backup Exec 2010 R3 sp2 version. It is the best most solid version.
If you are already using this, make sure you are using the Symantec drivers for the tape library.
you can also try removing the library from Backup...
I realize this post has been around for abit but wanted to let you know that it is a requirement for the BE Server to have FC connection to SANs
Backup Exec Support Tech