After upgrade TFS 2010 RC to RTM you might see a problem when you try to create a new team project. The creation fails with error:
Event Description: TF30162: Task "Queries" from Group "WorkItemTracking" failed
Exception Type: Microsoft.TeamFoundation.Client.PcwException
Exception Message: TF237195: The following user name is not supported: [SERVER]\$$PROJECTCOLLECTIONADMINGROUP$$
The answer is simple, but I had missed it!
Make sure that you are creating your new team project from a copy of the 2010 RTM version of Tem Explorer. If you use the RC version you will see the error.