Thank you for sharing.
But if you'd like to contact Adobe, you should click the Contact button at the top of this web page. All you're doing by ranting on this site is screaming at fellow users who are trying to help you out -- or, at the very least, help you find a program that will do what you need.
What is the source of these AV files, i.e. camera used and also the method that you are using to "Capture" these files into PrE?
Also, whatever you do, do not use DivX, or Xvid for any conversions. Those are delivery-only formats, and will not edit well, if at all. Stay far from those, except as a delivery format/CODEC for the finished movie.
The videos were from a Canon camera (I don't know the model)
and they weren't captured - they were copied off the SD card to my pc.
They're all AVI files.
They were all shot within 2 hours of each other.
Thanks for the info.
Just as a test, get G-Spot and run one of the files that does work, plus one that does not work. What is the difference, if there is one? Hint: a screen-cap of each in G-Spot will really help and save a bunch of typing. Use the little "camera" icon in the lower-middle of the forum editing screen's toolbar to attach these screen-caps, so they can be quickly seen and compared, and so they do not have to go through queue. There might be something there.
This is just a guess, but I'd say that there has to be a difference between the files that work, and the ones that do not. It might be something like auxiliary files not being copied over from the folders on the SD card, or similar.