Sync problems audio-video

I have a cheap TV-set next to my computer. It has a SCART output that I can connect to my PC. Now, if I watch TV on my computer screen (via my capture software) sound and video are in perfect sync. However, when I actually capture the video and audio the resulting mpg file has a serious sync problem (almost one second out of sync). The timing error seems to be constant and is not getting worse during time. Can somebody explain this?:confused:

Please read before posting: look at dropped frames Thanks BaronVlad

My software tells me: 0 dropped frames.