Avisynth, Virtualdub w/ Digital Capture Help?

[Celsitude]

I hope someone can help. I'm capturing from digital satellite in Virtual Dub with Win2k. I capture to avi in Huffy and the file is about 20gb. The problem I am having is this, If I load the file directly into AviUtl, the screen goes blank after about 4 minutes - so I tried instead with Avisynth -> VirtualDub. The odd thing is: when I load the captured avi (the original 20gb file) I can scan through the whole file without a problem - i.e. I can see each frame, but when I load the avs file into Virtualdub, I can only scan to about 4 minutes into the file and then it freezes on one frame - this is without any filters at all - only avisynth greedyHMA, and even without the greedyHMA filter. Can anyone explain what is going on? Suggestions? I'm completely stumped.

Thanks for any help, Cels