Backup Exec 12.5 intermittantly hangs on back ups/byte count stops

Running BE 12.5 rev 2213, all updates installed. Byte count on both the tape and hard drive have not incremented in a day from 200,800,142,622 (bytes). This happens from time to time. A reboot of the server usually fixes it. I restarted the BE services with ServicesMgr.exe and same thing happens. No media alerts to remove a tape (as per this thread). Tape drive is an HP LTO Ultrium-2. I read someone upgraded their SAS controller driver but I'm not sure if that'd help me.