In the past couple of days, I've twice had the page Hammerfest was on spontaneously reload, causing me to lose my game and all its data. Tonight it happened on level 87, after nearly an hour of playing, and merciful heavens was I ever unhappy

I'm 100% certain that I didn't reload the pages by accident -- my hands were nowhere near the R key, and the mouse pointer was in the center of the Hammerfest screen the entire time.
I actually lost a third game yesterday, when I pressed C just as I was entering a PD and it caused the game to crash.
I haven't seen errors like these before, so I'm wondering whether they've started happening to anyone else. I'm using Safari 5 on a Mac, OS 10.5.