left it running overnight as usual, woke up in the morning to black screen (not surprising, my display sleeps after 10 minutes) and fans on full blast, and no response to keypresses etc - was forced to do a hard reboot (hold the power button down for 5 seconds to turn off). I installed snow leopard on my (first gen, core duo) macbook on friday, clean install on a brand new hard disk then copied most of my apps/files/settings over manually from the old leopard hard disk. I'm not blaming this one directly on transmission, but i thought i'd post here in case anyone has had similar experiences or has any suggestions.
Edit: turns out my particular problem was nothing to do with snow leopard, or transmission