Hi Paul,
My problems ultimately related to i/o perfomance on the Netgear platform. It had a couple of bonded GB interfaces, but the platform itself was busy with a VMFS partition, NFS and some CIFS. Often the VDR jobs would run fine, but running a scheduled program, which would instigate some concurrent jobs just saturated the box and VDR would fall over. I discovered this without raising the SR in the end.
As a result, I have given my VDR a dedicated LUN from my EqualLogic SAN (not massively cost effective, but cheaper than the headache of not having a vSphere backup!), presented as a VMFS (not RDM) LUN to my VDR appliance.
All running very smoothly now, and with the dedupe, usage not nearly as high as one would expect.
Good luck with your issue Paul.
Best regards,
Gavin.