From Mexico.purplecow.org
The Growl
Aaah, man, this camera shits me sometimes. I'd swear it quietly changes custom function settings when I look away. It seems to set a mode where you can't change the AF point. Grr.
How it should work by default
The normal procedure is to tap the AF points button and then use the arrow keys on the back to select the AF point (try doing that while looking through the VF).
CF manual extract
Custom function 11 impacts this. And since I can never find the manual in a hurry, I give up and: