Analog capture quality

[qwe123]

Trying to capture in VS7 analog HI8 video through Hercules Video Action card, in a sempron 3000+ computer (120G HDD, ATI 9250 card, 512MB memory). When the filmruns on the screen, before capturing, it looks fine. When trying to capture MPEG2 in the higher resolutions (PAL 720*576) the movie is distorted, jumpy - with horizontal lines - even though I followed the recomended procedure I found in this site. In AVI, its the same, even worse, and sometime the movie even freezes. In SVGA, the picture is a little bit better, still not the best. Any idea what to do?
Alain