The a clip of the "after" would show me the problem. But do you also have a way to clip a piece of the original mpeg, before Vdub resizes it? You could post the clips to mediafire.
I have tools that could check the original HD mpeg clip for funkyness. For instance, I'm wondering if Premier is exporting it as 30p, or if it's trying to make it something interlaced. Or the tools may show something else strange. Does the problem show up before you resize? What's it look like when you step through it (unresized) frame by frame? Do you see signs of interlacing? Are you using an mpeg2 plugin for Virtual Dub? What resize method are you using?
Anyway, while you're waiting for me, you need to try substitutes for VDub 1.8. Maybe VirtualDubMod or VirtualDubMpeg or just an earlier version. Your's might have a bug that they didn't catch, because, for example, it specificly hits 30p at a certain resolutions.
And see if you can get some other way to capture from the camera (a free trial?). I know CapDvhs does some digital video cameras, if there's a "driver" for your camera. (I'd give you the links, but I gotta split).
We can figure out what's going on, sooner or later. The problem is, I suspect you're pulling your hair out, right now. You might be on a deadline. And I haven't had any experience with HD cameras, or their files, or Premier, or some the tools that people mention using for their HD cam files. You stand a much better chance of nailing down the problem, quickly, at Videohelp forums . When we blaze new trails in video editing, we go there to solve the numerous obstacles in our way. They are the best video techeads around. (Some of them write video tools). And they have a couple of forums about working with video from HD video cameras.
They are more cooperative if you search their forums, before asking. Of course, their search is broken, like most forums that tell you to search first. :) So when you don't get any real search results, repeat with their Google-search link (e.g. "Click here to search for 30p premier m2t using Google in our Forum."), and wade through Google's false hits, and end up with a lot more good hits than their own search engine found. :)
If you don't find anything by searching, you could post to a forum that seems to fit. Like "Advanced Video Conversion" or "DV / HDV".
They might ask for a sample clip, and you'll already be set. :)
Your familiarity with the videocam stuff would make it a lot easier to tell what's going on in their discussions. When I read one like this post, I can see they're talking about an m2v, which is a demuxed mpeg2 video file. But if they hadn't mentioned m2v, I wouldn't know if maybe they were talking about a .dv file. And I don't know if they're talking about editing or capturing.
Anyway, I'll try to help if you still need it. But it'll go quicker if we're both searching videohelp and stuff.
And I'd like to know how it turns out. Sometimes I never find out what happened, and it's unsettling, ya know?