My GLC is currently in the shop for a software update - estimated to take 7-9 hours!
Last Wednesday, the screen went black when I started it up - radio was putting out sound, but I could not set nav destination, select phone screen, choose media, etc. As I had to pass the dealer on my way to a meeting, I stopped in and was told that since I picked the car up at the factory in April, there was 'a stack of DVD's' that needed to be applied to the system. The screen then came on and worked over the weekend. Dropped it at dealer Monday morning, got a call late in the day indicating that after the update had completed, the tech got a message that the screen needed to be replaced - now waiting for the part to arrive, should be in today.