Have you tried to “Verify Game Cache” in steam? Also on latest AMD drivers? I’ve read various things around here that ATi has a few issues with TF currently, one being the Texture Compression. But that is after your game starts.
Try to verify cache, if that don’t work, try a re-install of TF.
EDIT: hehe mikael beat me by 1 second 😉 A+ dev support!
