Garbage frames with NanDub

[mironto]

Lately I encountered problem through encoding with NanDub 1.02. Not only I get about 3 freezes in a movie after encoding (which can be removed by checking antifreeze in encoding options), but even with no freezes, there are some garbage artefacts which look same as if there was freezed frame and picture gets jerky till next keyframe. I cannot get even 5 minutes of clear picture, and it's driving me mad. I thought this happenedas I switched to WinXP/Duron 1.3, but I tried it on old config where it worked before but the picture still gets corrupted. The only thing that comes in my mind is that I changed some encoding options in NanDub that didn't use before which causes this behavior... Does anyone encountered same problems or knows of some option/combination of options that can damage picture?
please help