DirectX 9a is buggy and updating to 9b fixes a lot.
I'm not too hot on analogue convertion but it may be the capture is set to mpeg NTSC and not PAL. May be worth trying the Pinnacle capture utility as well.
Other things to check:
Use EndItAll to close off all non-vital b/ground progs click here (as av, firewall, system restore etc can interfer with capture or drop frames.
Check DMA is enabled on drives.
Also try updating your card's driver.