For the past couple of days I have been unable to create a backup of the systemstate on one of my DCs. VSS produces the following error whenever an application (be it MS DPM, BackupExec or NTBackup) tries to use the Volume Shadow Copy Service. The error in the event logs is:

Code:
Event Type:	Error
Event Source:	VSS
Event Category:	None
Event ID:	20
Date:		9/22/2009
Time:		10:00:21 PM
User:		N/A
Computer:	
Description:
Volume Shadow Copy Service error: A critical component required by the Volume Shadow Copy service is not registered.  This might happened if an error occurred during Windows setup or during installation of a Shadow Copy provider.  The error returned from CoCreateInstance on class with CLSID {faf53cc4-bd73-4e36-83f1-2b23f46e513e} and Name VSSEvent is [0x80040154].
followed by:

Code:
Event Type:	Error
Event Source:	VSS
Event Category:	None
Event ID:	8193
Date:		9/22/2009
Time:		10:00:21 PM
User:		N/A
Computer:	
Description:
Volume Shadow Copy Service error: Unexpected error calling routine CoCreateInstance.  hr = 0x80040154.
I've tried searching for solutions and so far nothing that resembles the exact error or a fix.

Has anybody come across this before or has anybody got any suggestions?