I eventually got through and Firefox 3 wasn't even on the site at the appropriate time (
maybe they took it down to limit downloads? nothing listed on their blog status). The site keeps going down. Hope they bring it up soon, they were putting a lot of marketing into the whole world record download within 24 hours.
As a partial defense to
Mozilla, they did mention that you cannot use the self update as it won't count towards their record keeping. But it probably still shouldn't crash, eh.
Update: Finally got it downloading @ 2:00 PM CST (12:00 PDT). 2 hours late, but at least they still have 22 hours to go. Good luck!