virtualbox.org

HCT wrote:Attached is a zip file with 2 log files and a small video file demonstrating "flickering". Hope that helps a bit to get the problems solved..

Do you have tripple-buffering switched off in your graphics card's settings?

SHAME ON ME !!

Tripple buffering was enabled again. Problems are gone after disabling (Windows 8 and Windows 7 guests are OK now). Sorry for the trouble caused by me and thank you for your support.

Regards,
Helmut

HCT wrote:SHAME ON ME !! Tripple buffering was enabled again. Problems are gone after disabling (Windows 8 and Windows 7 guests are OK now). Sorry for the trouble caused by me and thank you for your support.

No problem You do not have to apologize actually because this is VBox fault that triple-buffering-on is not handled properly, and there are plans to fix that in the future.
Glad that your problem is now solved.