Hi !
We have the same problem, but only one client is performing bad.
This client have suddenly droped to 50 MB/s (No changes done). All the others klient is working fine.
Have tested to copy files to and from the client > Working fine
Checked the networkcard / switches for error > OK
Disabled antivirus
Disabled AOF
Running w2k3 SP2 on backup server and all clients.
Backup exec 11d 7170.