Oh, cool thanks! Interesting that you couldn't reproduce. I tried it again - finished a couple levels and hit Ctrl+R again, and again lost my saves. I'll do a little more testing around in different browsers etc when I've got some time, see if I can narrow it down.
Edit - actually just tried again, and my progress stayed. Okay, I'm not sure what happened. If I see it again, I'll try to figure out the reproduce.
Now to figure out 36...