I'm having a similar problem. If I click any of the uploader buttons, it starts to bring up the uploader screen, and then Firefox crashes. I can upload via FTP, insert manually, and then bring up the size/layout screen to adjust things. It just started happening yesterday and I can't come up with anything I did to cause it.
Something that could potentially help whoever might be looking into this -- I seem to be having this problem on multiple WordPress installations that are on different servers. Also, the problem is happening on multiple *computers*, as I've had the crash happen on my office and living room computers. The computers are on the same network, but I doubt that's the issue. It seems to be some way that WP is interacting with Firefox.
Interestingly, the uploader appears to work in IE7. I can use that as a workaround if necessary, but it's a pain in the rear.
This doesn't appear to be a plugin issue with me, by the way. I disabled all plugins in one of my WP installations and it still crashed. I also have closed browsers, deleted histories, and restarted computers ... no luck.