It never skipped on the rear cog. This is how I discovered it: I'd come down a hill in the big chainring, then when I'd start up the next hill, I'd stand for a few strokes (still on the big chainring). This is when it would skip, and it was skipping on the chainring.

I got home and took a look, and this is what I saw:



The chain was running on the top of the teeth ("skating"). That's when I measured the chain.

The chainring teeth are pretty pointy.