I promised earlier that I would respond with any information concerning a resolution to the playback problem I was having with my GL-2.
When the unit was sent to Canon for the second attempt at repair, the technician was ready with the necessary test equipment. And, once again, to the day, the GL was returned in a week (Not bad).
On this ocassion the "main CBA" was replaced and all is finally well once again. I have had sufficient time to check out the camcorder and playback has been normal. I hope this helps anyone with a similar problem although it does appear to be very rare. Now if I can just figure out what the "main CBA" is.