Running the Group Policy Management Console Modeling Wizard I get the message
"An error occurred while generating report:
The given key was not present in the dictionary."
There is a KB article which is utterly useless in figuring out what key it isn't finding - here.
I can get the actual group policy RSoP result successfully by running Get-ResultantSetofPolicy in Powershell on a machine with the policies applied but it would sure be useful to have this tool work (or to actually figure out that I really have a bad/missing key in the group policy database and which one it is).