dialog boxes don't respond to keypresses

Apparently all issues are required to be posted to the mailing list, so
here goes:
 
When, for example, reverting a file from the commit view,
a pop-up dialog box appears verifying I really want to revert 1 item(s).
 
This appears not to be the default Windows' MessageBox, and the Yes and
No buttons don't respond when I press 'Y' or 'N' on the keyboard.
(Ctrl+C to copy the message text to the clipboard won't work either I
suppose...)
 
Greetings
Stijn

  <http://www.spectorphotogroup.com/>