today a few times i found my n900 unlocked (with screen on) but pretty sure i locked my phone. So last time i checked for mail i double check the screen and keys were locked, but again was my phone unlocked.

G3 was on (but not all the time), sometimes the browser too. Slide was always (after locking) closed. I did install the camkeyd app (for using the cam key to open the 'switch running apps window').

my phone was in a case (which does have some magnets, maybe they interact with maemo or something...)