1) What program you using to export your footage from?
2) By my understanding the footage is fine before it gets exported?
3) Do you get any errors about the video after the exporting is complete?Some SolutionsFirst of all I think we all need some more detials to properly help you out
1) Try re-installing your editing software
2) Try different exporting settings
3) Check for updates for your software
What I always try to do i keep my video in always the best quality... avi format. Sometime I export out of premiere with the Microsoft DV AVI codec, its faster and still keeps it pretty good quality and you are able to bring it into AlamDV and other video applications that support DV to do further editing/effects. By re-installing it may fix that Microsoft DV-AVI Codec. Also what kind of machine do you have? If your computer doesn't have a decent video card, Pentium, RAM it may cause some problems.
Try re-installing the Matrox DV Codec...go hereftp://ftp.matrox.com/pub/video/DigiSuite/End_Users/release70/codecs.exe
Further Codec Optionshttp://graphics.lcs.mit.edu/~tbuehler/video/codecs/avi.html