2.5

Test for Brecht: this line makes drawing buttons fine. 
However note:

- redraws on lines 3107 and 3024 don't do anything
- tooltip timer is messing with redraws too, if you
  have tooltips on, it continuously sends redraws.
- I would code tooltip to reset on any mouse move, 
  and only start timer when mouse is still completely.
  That would make them appear much more quietly.

source/blender/editors/interface/interface_handlers.c

@@ -2766,6 +2766,7 @@ static void button_activate_state(bContext *C, uiBut *but, uiHandleButtonState s
 			data->autoopentimer= NULL;
 		}
 	}
+	ED_region_tag_redraw(data->region);
 
 	/* text editing */
 	if(state == BUTTON_STATE_TEXT_EDITING && data->state != BUTTON_STATE_TEXT_SELECTING)