This problem has plagued me for 8 months.
Avanced server, 2 gig ram 1.7 Ghz Supermicro, dual 450w power supply, battery backup- happens on Ver 8.5, 8.6, patched or unpatched,
no Mcafee, have Symantec CE but not thru BK, separate Adaptec channel for tape drive, autoloader and now a Sony DDS3 standalone. Never had a roll over before installing ver 8.5., for over a year
I now start Veritas from a .bat file in "startup", setting all Bkexec services to "manual" not "Auto". The Bat file is located in the \util directory on the Veritas CD or on Veritas site
Part of the problem involves a memory leak in BackupExec.
No other program I ever installed on this server caused a memory leak.
To counter this I run the "Bestop.bat" and "Bestart.bat" (on CD) thru the Windows scheduler once a day. You might be able to "Bestop" the bloody program until just before the scheduled backup and sometime after the backup completes. My server balks with this, so I Bestop and Bestart within 5 minutes. If you have the memory leak, you will notice BK and other programs release memory at this point.
BackupExec is not the only program which leaks while BK drivers are loaded.
Also went into my server BIOS and set all IRQ to auto and set the PCI bus to 32 time slice vs 64.
Two weeks without a roll over at this point. Usually minidumps, or rolls over ever 4 days. Minidumps without roll over mostly.