Can't boot into 4.9 after upgrade from 4.1 to 4.2

Finally I decided to upgrade form 4.1 to 4.2 but after reboot I can’t boot my server. Now grub shows 4.9 as default boot, but I have only a black screen without any messages. If I change to 4.1 in the first screen I can normally boot.
I already tried dpkg-reconfigure grub-pc without any results.
Could someone help me to find the problem?

A black screen was also mentioned in this thread: