Cannot perform backup to Sentinel, VSS Errors in Event Viewer

I have a WD Sentinel 4000.  I have 2 laptops that backup to it and both are running Windows 7 Ultimate x64.  One laptop backs up perfectly.  The other will not backup at all.  It fails at 1% and I have VSS errors in the event viewer.  This is the error:

Volume Shadow Copy Service error: Unexpected error querying for the IVssWriterCallback interface.  hr = 0x80070005, Access is denied.
. This is often caused by incorrect security settings in either the writer or requestor process. 

   Gathering Writer Data

   Writer Class Id: {e8132975-6f93-4464-a53e-1050253ae220}
   Writer Name: System Writer
   Writer Instance ID: {dc99b3de-ceb1-48d2-8669-8fd43de7fac9}


I have used dcomcnfg to ensure that Network Service has permissions on the laptop.  I attempted to reset COM+ using some tutorials online and I think I failed at that so I performed an upgrade install to return the computer to a working state.  I still cannot perform the backup.  I performed a clean install and still have issues.  I'm pretty sure that the correct permissions are there, but obviously I am missing something.  Any help would be appreciated.

Very respectfully,

James Shinevar

If you had a 3rd party backup before it can cause this.  You said you did a clean instal, you don’t mean the pc and it still fails?  Also make sure your WD box has all the windows updates applied