Kinda new here. I am using Sony Vegas 9.0 Platinum. The short summary of the problem: My footage, when imported into Sony Vegas for editing purposes, is perfectly deinterlaced, but when I make my final export (to .avi or .wmv), the video has interlacing all over the place.
More details:
I have tried this with numerous different kinds of source videos, with the same result. Now, from my understanding, it is bad to use divx or xvid compressed videos in vegas, so what I've been doing is using VirtualDub to convert videos either to uncompressed or HuffYUV before putting them in vegas. So somebody stop me here if this process doesn't really get rid of the divx/xvid compression and is the source of all my problems.
When I go to project settings, "Deinterlace" is set to "blend fields" by default, and this obviously doesn't solve the problem. So I tried changing it to both of the other options ("none" and "interpolating") and niether fixes it. Lastly, I have tried changing the order of the fields. By default, it's set to "lower first". I have tried changing to it to "upper first" and "progressive" but neither solve the problem.
Another thing to note: While editing the footage, The preview window is perfectly deinterlaced. It isn't until my final product that the interlacing issues occur. (Though, as the project is being rendered, and you can see the preview window kinda moving along with the render, you can see the interlacing problems at that point.)
I want to export to .avi, but I tried .wmv, and while it wasn't as extreme, the problem was still there.
Using WMM produces perfectly fine deinterlaced exports, but I don't want to have to be limited to that program. But this fact leads me to believe that it's an issue with Vegas and not something else on the computer.
I've consulted the major AMV guide hosted on this site and the other threads, so forgive me if I missed something. I originally had this problem about two years ago with an older version of Vegas, asked somebody for help who was into AMV editing but he was completely stumped. I figured upgrading to a new version of Vegas might solve my problem but it hasn't. So any kind of help is appreciated.

Perhaps a setting that needs to be changed? Everything should be at the defaults, I haven't messed with it much.
Thanks in advance.