Mac Carbon: Control on Caps Lock becomes sticky problem

[prestowk]

My Caps Lock key is mapped to Control (System Preferences -> Modifier
Keys).  It happens quite often after some typing that the Control
modifier (in a software sense) seems to get stuck, so that even if I
just type "a", it is interpreted as "C-a".  The only way to get out of
this state is to hit Caps Lock once, to turn off the Caps Lock LED
(which always seems to be on when this happens).

So, it seems to be related to Caps Lock's on/off property.
Unfortunately, it seems hard to figure out what triggers this.  It
seems to be triggered by fast typing involving key combinations
including Control (on Caps Lock).  It happens often enough (with messy
effects when typing fast: text is killed and rearranged considerably
before you realise what has happened), for me to be a major annoyance.
If anyone has ideas of what could be going on here, please let me
know.  Thanks.

Environment: Ibook G4, Mac OS X 10.4.4, Emacs 22.0.50.1 (Carbon Emacs,
macemacsjp).

p.