It took me awhile to realize that the notorious two-finger pinch-to-zoom feature on the new MacBooks and MacBook Pros was what was causing Firefox and Mail to freak out every time I tried to use the trackpad. Worse, you can't disable just the zoom; in order to disable it, you have to disable all two-finger trackpad support. The pinch zoom feature was horribly implemented, and should be either be killed off or modified to allow for selective enabling in specific applications.
Luckily, Jeff Hawkins came up with a way to disable pinch zooming in Firefox, Safari, and Mail. All hail Jeff Hawkins!