thx, not really one answer describes the same issue. I have noticed that when my altitude is below 10.000 ft. or so, the screen doesn´t smoke out. When I´m not in flight, the screen stays OK. When I have the problem in flight, I can always get a normal screen again by pressing shift-6 for external view and than W for cockpit view. This however only holds for 10-20 seconds, then the screen smokes out gently again.
Many thanks for responding so quickly:-)