Help: Very slow backup

Have a Windows VM Client (Windows 2003 x64) that has about 30GB of data in it, but it takes forever to backup. It renders a very low througput. Can you guys point me to the steps to troobleshoot this kind of situation?

My Master is a SLES 10 SP3 running NBU 7.1.0.4, no disk staging, backups go directly to LTO4 tape drives using fibre.