Updated today to 4.5.549 and the old blue-screen problem returned. :o

It has something to do with Avast.

Each update there is a new problem. ???

See also:
http://forum.avast.com/index.php?board=2;action=display;threadid=9350;start=0#msg78189

Is it save to stick to an old version (4.1.501)?

Otherwise I have to look for another Free Virusscanner.