While surfing the net reading news I came across a page at a Network World that crashes Firefox 3.0 on a 64-bit Ubuntu Linux system (a test platform not regularly used for day to day surfing).
The browser ID is as follows:
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9) Gecko/2008061017 Firefox/3.0
The page in question is __http [colon slash://www.networkworld.com/news/2008/073008-dns-attack-writer-a-victim.html__ and I tested it 3 times to make sure that it wasn't some sort of fluke. The browser crashed each time.
Does visiting that page crash your installation of Firefox?
Anyway, after checking I noticed that the system didn't have Firefox 3.0.1 installed, so I did a quick upgrade and revisited that page. This time the browser didn't crash. This particular system is rebuild from scratch about every 2 days, so I'll have to modify the setup script to make sure all packages are up to date.