COM Error on Upgrade to 10.1

I recently upgraded from arc 10.0 to Arc 10.1. I have an engine application that is now throwing a COM exception:

Retrieving the COM class factory for component with CLSID {DB2CDE6F-A264-4129-A4CE-99F9A47F1830} failed due to the following error: 80040111 ClassFactory cannot supply requested class (Exception from HRESULT: 0x80040111 (CLASS_E_CLASSNOTAVAILABLE)).

I have verified that CLSID {DB2CDE6F-A264-4129-A4CE-99F9A47F1830} is in the registry. I did a Repair of my install of the Engine SDK for .NET, but that did not help.

Any help would be appreciated.

The code it is trying to run is:
Dim oXMLStream As IXMLStream = New ESRI.ArcGIS.esriSystem.XMLStream