Occasionally, I see thin horizontal strips in the captured video that looks like they came from the last frame and green bars across it sometimes:

No one has a rock-solid answer for why these problems occur, but it appears to be caused by contention on the PCI bus, which then prevents the sound card and video capture devices from emptying their buffers in time. This problem is reported more frequently on motherboards that have a VIA chipset, or in systems that have a SoundBlaster Live! sound card. In the former case, try upgrading your VIA 4-in-1 drivers first, and if that is not sufficient, check for a motherboard BIOS update that specifically addresses your problem. As for the Live!, the Creative driver is known to cause problems by lowering the latency timer of the PCI bus. (The result is similar that of making the red lights appear every ten seconds at a four-way intersection.) In that case, try installing the Microsoft drivers instead.