Black Hole
May contain traces of nut
Check to see if you have both types of remote and swap them over. It has been posted that one does it the other doesn't.
Edit.
Customised Firmware 2.10 (for 1.02.27)
Both types flag up when you change mode, but only one type complains if you press an invalid button for that mode (why the heck...)
Update: belay that. Only the MDB type (programming requires 3-digit codes) flag the mode change, and the "invalid button" is only for modes that have not been programmed at all. The ADB type (4-digit codes) does not output during mode changes so does not flag anything. However, some MDP type handsets are incorrectly labelled ADP!