Very slow file level back-ups of Hyper-V virtual machine

Recently I had a Windows 2003 32 bit server crash due to a RAID failure. We run DoubleTake Recover Now as a DR solution. Using Recover Now, a Hyper-V virtual machine was created of the failed server, and we were back in business within hours. Everthing runs well with the exception of my back-ups. Backing up to an IBM LTO tape library before the server crash used to average between 700mb-1000mb/minute. After the crash, the virtual machine took a 50% hit on backup throughput (about 400mb/min). I exported the VM to another Windows 2008 64bit hosts server to see if throughput would improve, and now the VM averages 200mb/minute. The orginal Hyper-v host had other applications running on it. The current host only runs one other VM and nothing else. Both are fairly new new IBM x-servers with plenty of memory (30GB and 24GB respectively).

I run Symantec Backup-Exec 2010. I tried both disk-to-disk and tape back-ups, as well as other virtual machines, and it is only this one VM that has the slow back-up problem. I spent a few hours with Symantec tech support and I am confident the problem isn't BE. Also, copying files to and from the VM via shares and mapped drives are fine.

Any help in solving this mystery would be helpful. If I can't get this problem solved very soon, I will be forced to use DoubleTake to revert this VM back to a provisioned physical server.