hey, that happens to me too, the falling down part on hills. I truly can't unclip once I have committed to climbing the hill...so, I just pedal as hard as I can, but sometimes the power runs out (I'm usually standing by this time) and the pedal refuses to move and... BOOM! I've tipped over to the side! I pray that this never happens on a busy street, as I'd be toast.

I am afraid that this makes me very uneasy when I have to tackle a new hill. My hands sweat, I pray feverishly, maybe swear a little too (under my breath, of course) and worry the entire time as it seems to happen without warning. I also worry that the chain will fall off if I shift gears mid climb. That happened once too. Just writing this makes my hands sweat!