After a few frustrating days of having the WordPress (flash) file uploader crash Firefox on every attempt, I finally stumbled across a (hopefully short-term) solution: disabling the Firefox Google Gears extension.
The strangest part…the issue seems to have come out of the blue. Who knows – maybe Vista Service Pack 2 is to blame?! Although, as much fun as it is to blame Vista, in all fairness, I did have the same issue on my older XP machine as well.
It’s not clear where the fault lies – is it WordPress, Adobe Flash, Google Gears, and/or a Mozilla Firefox issue? – but disabling Gears seems to be the best solution @ the moment. Hopefully one of the involved parties will figure out how to prevent this from happening, sooner than later.