Sony Vegas 8.0 and 8.0a had a problem with targa sequence files (artifacts) in a video compositing. The bug was fixed in this new update, Vegas 8.0b. Unfortunately, this time, what was happening with the targa sequence files is now happening with the audio tracks!
If you have a project with some audio tracks, some tracks don't play or don't render at all. Some other audio tracks play but stop playing all of a sudden.
Let's hope Sony can fix Vegas once and for all when they release the next update - the future version 8.0c. Anyway, the software is OK but if you try to make complex projects with more than 3 or even more audio tracks, you'll notice the BUG and as far as I know there's no workaround for this one. Here's the *.jpg file I've sent to Sony in order to show them the problem.
Cheers,
Mark