X on ThinkPad X220 with chrome or firefox goes blank

Hi,

I updated my notebook over the last couple of days and have now
problems starting chrome and firefox. The effect is that the screen
turns blury leaving hard to recognose characters on a white screen
after starting any of these applications.

I can use Ctrl-Alt-F2 to come back to the terminal. Of course, this is
now a flight in the dark. After entering Ctrl-C and restart X, I get a
new X running until I start firefox or chrome again.

Applications like Claws Mail, Arora or xterm work without problems.

I do not see anything different in the log file of X.

Does anybody have a clue what could cause this?

I will recompile and reinstall all my ports now to see what will come
out there.

Erich