13.2 booting to black screen on MacbookPro (radeon)

Hi there
I’v just installed 13.2 and all went smoot, but i’m experiencing jsut this little issue.
It boots correctly (from EFI. Very fast!)
The annoying thing is that i have to CTRL-ALT-Fx and then CTRL-ALT-F8 to get the KDM screen, otherwise it just boots to a black screen.
Anyone having the same problem?

Apparently it is due to the system not Being able to set the brightness correctly on the first kdm start. I tried to install fglrx drivers with 1click but that leads to a dead X session so I reverted.
If I start the system in recovery mode, all works better. I think is something related to composition. Nobody has some hint?