Did a few searches of various Sorted Groups - got reasonable results. Started an Unsorted Groups search; a Critical Error Message dialog instantly appears with a few occurrences of this message:
[23:59:25] ERROR - Resolver: Unable to open Source Data file
The search result list is not updated from the first search. Apparently the error is a show stopper.
The Unsorted Groups' spool area contains 10 groups, ~1-2 GB of data.