So I just bought Sam and Max season 3 from your website, and I downloaded episode 1, only to find myself subject to a rather... odd graphical error. Here are some examples, though it occurs elsewhere:
Note Skunkape's lack of eyes here.
Max appears to be missing his eyes, teeth, and the inside of his ears.
I've tried it with the graphics at 1, 2, and 3 (the highest I can set it to), as well as both fullscreen and windowed. Nothing seems to help.
I'm running this on a computer with a Pentium 4 2GHz processor, 2GB RAM, and an ATI Mobility Radeon 9000 with integrated video memory (32MB physical, but I only ever seem to have problems with games that require over 128). Season 1 (bought via Steam) runs just fine, and I have yet to try any other Season 3 episodes.