Thanks for your comments and suggestions. However, I don't think that the issue is related to my display adapter. The problem only occurs with live tv and new recordings. If I watch recordings which were done before last Sunday (when I installed Vista), they work fine. Live tv looks like there is a short loss of signal once in 10 seconds or show. I never saw this behaviour with XP, so I suspect there might be something to change in my Vista configuration.
Attached is a log, I did a brief test around 17.3.09 19:36.
Attached is a log, I did a brief test around 17.3.09 19:36.