If it is dark in all areas (entertainment, climate control, navigation etc.) it will most likely be the screen itself, but the screen and the computer that drives it are both on the teileclearing list so the techs can't just throw parts in there... they gotta
get BMW authorization before replacing them which can be a pain in the butt sometimes.

Dealer replaced mine...
 

I had this issue of the screen not turning on. I dealt with it for many months. It would come on after stopping, turn ignition off, back on and it would work. I finally took it in one morning after it didn't turn on. I drove straight to dealer and left X running. Had the service tech come out and see that it was not working. He ordered me a new one on the spot and scheduled to replace it when the new screen came in. No probs since replacement.

The screen itself was the culprit or was it the unit with a bulb, etc.? They just finished a reprogram today hoping that was it... they couldnt reproduce.

Yours was still working - as in you can see idrive functioning with a flashlight at least?

My screen was dark twice. When I took it in to dealer, they say they "fixed it". The service note says "Correctedby0000555: (6583000200 "

I haven't noticed the problem re-occur. I will follow up with my dealership and ask them what this cryptic note means.

Jan 10 update: Still no response from my dealer yet as to how they "fixed" it. I haven't seen a reoccurrence of the problem yet though :)

Jan 14 update: Heard back from my SA. Basically, there was no fix made as the technician was unable to duplicate the condition. :( I'm not surprised that they were unable to recreate it as I've only seen it twice so far but the service note should not have said "Correctedby...".

NAV screen
 

My screen actually had died completely after that. Between the time I took it to dealer and the fix, my screen never came back on . It wasn't visible at all. Not even a dim image was visible. It started out that way (where I could see a dim image). Eventually, after a few months of "dealing with it" the screen died.

Jan 26: My IDrive screen was "dim" today (not "dark"). I drove straight to the dealership.

Their head tech looked at it to confirm. He did no tests as he said that no faults showed when I had previously reported it being "dark". [After he left, I turned the car off and back on, and the screen was back to normal.]

They are going to replace the screen (the "CID") and then re-program (a 1 to 2 day effort).

Jan 27 update: It's not going to be so straight forward (as what I said above). The service department have been "running tests on the car all day" to determine what the faults are. These tests are continuing. They now say that they want to be sure that the CID needs replacing as BMW has to authorize. (I'm not surprised that they are doing these tests and that they need BMW authorization but the head tech had said they were going to replace the CID... That's what's disappointing.)

Mine has been this way for 3 days. I'm making the service appt now.

Just for the sake of thoroughness...

After the re-program, my screen has still done this twice on mornings after a night in the garage so it's not the temperature. At one point before I had brought it in, it had been dark for 2 weeks straight, even after restarts... and it magically started working again a few days before I brought it in so my dealer never saw it fail. I told him about it via email when it happened again and he hasn't responded. I guess I'll have to break out the camcorder hoping to catch this again. I'd like a new screen for sure. Seems like a bad batch. The other thread mentioned a bulb though... dunno.

As previously posted, my screen was dark twice late last year and then dim once this year.

When I took it in to the shop on Jan 27th, I had shown them that it was dim. After restarting the car, the CID was operating normally.

The following is from the shop's notes:
Performed short test with ISTA but no faults for CCC or CID showed up.
Performed test plans for CID background lighting and for CCC malfunction. Both ended without faults except the CCC test plan stated that over or under voltage can cause sporadic failures with the CCC.
Switched over to DIS TESTER and performed further tests. That test still showed the CID as O.K.
PUMA case submitted. R/I center dash vent assy and CID. Found the LVDS cable slightly kinked. Replacement of CID was recommended.

So they replaced the CID and re-programmed the car. I know that they had to wait to get approval from BMW NA for the CID replacement so they had the car for 3 days.

What's interesting is that the screen is brighter than before. I have always had it set to default Brightness (middle setting) and that's where it's set now. Definitely brighter. Not sure if it's sharper too.

thanks brian... can you clarify which the CCC and CID are so I have some idea of what I'm talking about when I refer your notes to my SA? ;)