Update: First of all, thanks for all who commented or sent me an email. I finally narrowed this down to some sort of issue with the USB ports on the machine. Uninstalling the drivers, then allowing Windows to find them again resolved the issue. Totally weird, but now everything is working great.
I took a bunch of pictures at a friends baptism this evening, over 75% turn out like this (though not all the same pattern).
I used two different lenses with the same result, shooting both in full automatic and 100% manual. When I open directly from the Compact Flash card in Photoshop I get: "This document may be damaged (the file may be truncated or incomplete). Continue?" I noticed it earlier this week on a few images out of hundreds, so formatted the card before taking the photos tonight. Update: Tried a different CF card -- probably 1 out of 33 images non-corrupted. Yikes!
Any photography buff have answers? Is there any way I can recover these files? Luckily I usually shoot at least 3 frames of each pose, so *believe* I got enough of the event, but it was very discomforting to know I might not catch any of the next one.