Adaptec 39160

I have a PowerEdge 2900 server running Windows Storage Server 2003 R2.  When I run backups with Backup Exec 11d, the throughput rate is awful  (120MB/Min).  I'm thinking that it is the SCSI card, but I'm not sure.  I looked on Adaptec's website and it doesn't list it as being compatible with Storage Server.  I also tried to download the latest firmware for it, but it errored out upon installing saying that it wasn't compatible with x64-based systems.  Can anyone tell me if this particular card is compatible with the OS?

 

The only thing that has me thinking that it may not be the SCSI card is that when I run a backup to disk, that is slow as well.  No disks are attached to the SCSI card.

 

One more weird thing...when the server is rebooted, the backup seems to run extremely fast (2,000MB/Min).  However, give it about 15 minutes and it goes back down to 120.  There are no indications of errors in the event viewer.

 

I've tried reseating cables, different tapes, updating firmware on tape drive, downgrading firmware on tape drive, changing channels on SCSI,  nothing seems to work.  I'm working with a PowerVault 122t autoloader.  The only thing that I can think of now is to replace the SCSI with something different.  Any ideas?