I habitually run a two-monitor setup with my main monitor in portrait; it's driven from a GeForce 6600 GT set to 'Rotate 90 degrees' in NVRotate, 1024x1280px, 32bpp colour.
If I start the Sam and Max demo with the monitor in this mode, then it first displays blank black (when it would be showing logos) then blank white with the credits music rolling... but nothing but white displayed.
If I change to unrotated, it displays fine.
I know "I would buy your product if..." posts are a little weak, but seriously - I enjoyed the demo enough to pay $9 for the episode, but not enough to rotate my monitor both in settings and also physically before and after each time I play it. If there's a way to fix this, I'm in.