Hi WOK,
(Would send this by email instead of boring everyone else with it but I couldn't make it work ......)
I had also heard some say that the new xpdr. handling could be interpreted as needing to keep 0000 until the before TO Cx., which is a pain as you say, so we mentioned it on the sim. the other day. The official word is that 0000 is only needed before you get the clearance and the code is entered on receipt of the clnc. as before. 0000 is there as an obviously "null" entry to make it clear that you haven't entered the correct code yet. I try to remember to write the code on the t/o proforma anyway because I've had the xpdr reset itself during taxi and I don't like scrabbling for the comms. log at lineup either!
Hope that helps.