Civil 3D 2010 ribbon crashes

[chhodge]

I'm having a problem getting Civil 3D (standalone) set up on a new workstation. The Ribbon is broken.  I have tried the posted solutions (workspace switch, repair install, re-install)  all with no effect.  This occurs with a default installation and no customizations.  The OS is Windows 7 pro 64-bit with all microsoft updates installed. 

Civil 3D installs and updates normally to service pack 3 with no error messages.

Opening the program throws the following error during the initialization process:

(Autocad pop window appears)

"Unhandled exception has occurred in a component in your application.  If you click continue, the application will ignore this error and attempt to continue.

Object reference not set to an instance of an object."

clicking DETAILS yields the followign text (in part):

"************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an object.
   at Autodesk.AutoCAD.Ribbon.RibbonPaletteSet.LoadRibbon()
   at Autodesk.AutoCAD.Ribbon.RibbonPaletteSet.Initialize()

...

(see attachment)

Help?

Thanks,

CHH