Messages on the AUGI Revit Architect and Revit Structure forums report an error that since the switch over to the year 2008, you can no longer save out your groups.
Here is the posted Revit Support Team response:
I apologize this issue is occurring as I know it must be frustrating. A workaround for now is to change the system clock to a month other than January 2008. The underlying issue for this case is being addressed by our development team on a future release. I am going to place this Support Request in a status called 'Pending Change Request.' It will not be closed and you will be notified when the enhancement has been implemented
Best Regards, Autodesk Support Team
Thanks to Thomas E. Maleski, Structural Designer and Autodesk Implementation Certified Expert for his posting on this matter