I've been trying to solve this problem for hours, so hopefully someone can help me!

I've got a copy of Sony Vegas Pro 8.0 (not a trial) and the clips I'm trying to play have been ripped from the internet using vixy.net, selecting the .avi option when downloading.

When I play the clips with an .avi or .mpg extension directly from the media bin, it works fine in the preview window. It also works fine when I play them in other programs such as Windows Media Player or VLC.

BUT when I drop them into the timeline, and preview them from there, nothing! However, I see clips with other extensions (.wmv, etc.) on the same track just fine! In the timeline itself, I can see the frames of the clips. No errors pop up from the program, either.

And what is most confusing is that these clips were working the last time I used the program yesterday. It's just all of a sudden that they are previewing black.

Any ideas? Desperate!