Argh! kernel.dll is *killing* me!

I don't know what gives here. I'd been making a few library file changes and testing them out when I started getting CTDs. So I undid the file changes. Still CTD. I copy and pasted kernel.dll from my main, untouched folder. Still CTD.

Any ideers what the heck is going on and how to fix it? I would have assumed copying kernel.dll from my main folder (where the game does still load and run) would have fixed any possible file corruption, but that doesn't seem to work.