Quick Control Screen fix

The Quick Control screen on the EOS 50D and EOS 5D Mark II DSLRs makes changing settings from the rear LCD screen quick and easy. However, if you are trying to use the Quick Control Screen and it doesn't seem to be working, it is most likely because you have the Custom Function for AF Point Selection method set. If C.Fn III-3 is set to Option 1 for Multi-controller direct, the Quick Control screen function will not be accessible. Unset the Custom Function and you can use the Quick Control Screen again.
Camera settings
Custom functions
EOS 5D Mark II