I used to get that error all the time, and still do sometimes.
Your computer is most likely having a hard time working with the avisynth files. Since working with them takes a lot of memory and computer dedication, your computer will often rebel by giving you errors like that or some brightly coloured orange screens in place of where your DVD-quality pictures should be.
Go easier on the computer; I had to edit my latest project in twenty second long sections because Premiere went too slow otherwise, or it would give me an error like that. Or, you could just export it in sections using the workspace bar. After you are done editing each section; you can stick them all together (append them) in Virtual Dub. This makes the video MUCH easier to work with since it doesn't go so slow that way and your computer can actually handle it.
Sometimes I still got that error when I was editing in sections; in that case just closing Premiere, waiting a few seconds for your computer to get its memory back, then opening Premiere again before trying to export the timeline once more usually fixes it.
The thing that really fixed it for me was using the work-on-project-in-sections method. It helped run Premiere much, much faster.
BTW, shouldn't this be in Video Help or Video Software Help?
Anywho, those are the methods that worked for me. Hope they help^_^