Windows and radio will not work

Alright ill try to make this as sort a possible. I have a 99 Pontiac Grand Prix GTP. With in the past 4 months off and on the radio will cut out and the windows will not work. I brought it to my mechanic twice. Each time the radio and windows would not work, but when he went to look at it they were working again and he cant figure out what is wrong. Any one have any ideas on whats causing this?

Is it all the windows or just one that do not work?

I am new to Prixs but not new to cars, so I would have to research as to what kind of modules are on the car. The Body Control Module, it may be at fault.

It could be something as the wondow breaker on the fuse panel inside the car, or broken wires that lead from the A pillar to the door.

It's all the windows. As soon as the radio goes out they stop working. They were not working last night but are working this morning. They must have went out like 20 times. When I shut off the car and restart it sometimes they would work. Someone said something to me about the time delay mod located behind the dash may be at fault but the interior lights are fine

Hummm... Not sure what to say. It definately is a loss of communications thus why it is intermittent but I am stumped.