Hello, I have exacly the same problem.
I own a european AVIC F900 unit. For one year, no problem. And on day, a black screen after startup, and then nothing. Just black screen.
After some testing, when keeping the map button pushed, the screen comes back.
I recently decided to go for the 2.009 european update. The update went fine.
But now, when I am trying to go on the MAP section, I can't go in. Eventually, it reboots.
Finally, I have checked the version. It says : no map version.
Somebody help please... ? Thanks.