Libraries are my first recourse when solving a problem (you should see some of the hoops I jumped with Frozenbyte support over the libraries included with their games), but alas that was not the case here, as I had already confirmed.
Thankfully, your second suspicion proved correct, and after replacing the shaders all three games run beautifully now. I am grateful for your help, despite having to sit on this issue for the past week and a half.
One question now remains - is this just my copy, or does it affect more Desura users? After all, I downloaded a version from both the Desura client and independently through the Desura web store, and both had issues. There might be something more going on.