A/C keeps running & stereo display doesn't appear
 

I have a '03 G35 Coupe and I realize that the first year had electrical issues and in the past I've had to reset ECU by disconnecting negative battery terminal. This usually solves the problem for a few months and then the problem crops up again. This time though the removal of the negative battery cable and pumping of brakes or removal of negative battery cable for more than 8 hrs. isn't doing the trick. I'm suspecting something else might be amiss. Also I've tried detailed ECU reset procedure with no success (i.e. light doesn't appear). Any ideas or suggestions besides bringing it in and getting ripped off.

Check TSB for faulty radio issues ! Sounds like you radio is gone !

What does TSB stand for.

Radio still works by using steering wheel controls. But LED display doesn't appear nor do buttons on actual radio work. Very odd.

TSB = Technical Service Bulletin

Your radio needs to be replaced, common problem in older G's.