Run button grey's out Post successful execution (running with Cache turned on).

Yes, you are right: the Run button is greyed out after successful execution of a workspace. (If you want it to run again anyway, you will have to use the option Rerun Entire Workspace (or Shift+F5)).

From the screen dumps you have provided I would say that the SQL operation has been executed but did not return any results. Could that be true?

To investigate the issue you could have a look at the Translation Log. And what happens if you execute the query directly on the data source? Does it return any records there?