Go to the website giantbomb.com with the latest nightly (since JaegerMonkey merge), currently 20100914 (Win7 x64), and after a few seconds, toward the end of the load, the page will hang and you'll eventually get the unresponsive script pop-up warning. Specifically it references: Script: http://media.giantbomb.com/media/vine/js/mootools-1.2.4-core-nc_10004.js:1 This worked (works) fine in Firefox 3.6.9, and works fine if methodjit for content is disabled, or you start in Safe Mode (has the same effect of disabling methodjit). Regression window is definitely since JM merge. Began with the very next build on the 12th.

You are using mozilla-central nightly 20100914, correct? The bug has been fixed in TM, but it hasn't been merged to mozilla-central yet. You could try a TM nightly if you want.