Elite Forces is the GBC-only game, not to be confused with the earlier B&W GB game.
And I'm kind of interested about the technical details too, but I can't quite recall reading about the specifics. Maybe it had something to do with the cart's save RAM?
EDIT:
http://www.gamefaqs.com/gbc/196763-b...ces/faqs/30432 says that the glitch can also occur on a GBC, and at
http://www.romhacking.net/forum/index.php?topic=10631.0 there's someone who can't even get the game to start on an AGS-101. Maybe it was just defective hardware rather than some kind of GBA incompatibility.