Missing pictures from download

I have a 20D and I am unable to download pictures taken in AV mode. All other
pictures have downloaded. I am able to view them in my camera viewfinder, but
unable to get out of the camera. Please advise. :)

I'm really not sure about this but since there are no replies, I've got a couple of questions:

1. Are you downloading your card directly from the camera, or putting the card into a card reader?
2. I'm not a Canon guy - is AV mode the same thing as aperture priority? I can't picture (pun intended) why it would matter if a shot was taken like that, manual exposure or whatever.
3. Is there any other part of your workflow process that changes with AV shots? Are you maybe downloading differently, and the shots are being saved in a different place in your computer?

Already posted about this in Brotski thread and should try what happened in that thread first, seems to be exactly the same thing and this is just a thread that should be removed as it is current in the other thread below.