ok. i've managed to crash safari 4 out of 5 times doing this, so it's *almost* classifiable as 'reproduceable:
have three tabs open in safari, it doesn't seem to matter too much what the first two are [i think i used macnn and macupdate] but open livejournal in the third tab. when the tab has loaded close the tab. does safari disappear without a trace [not even an "...unexpectedly quit" message from the finder]?
i've tried it with a few combinations of tabs but livejournal in the third tab seems to 'do it' for me [as mentioned above] four out of five times.