I’ve been having a problem with slow response from Firefox 2 on one of the PC’s I use. Pages would stutter just before finishing loading and opening empty new tabs was slow. Occasionally Firefox would crash hard while loading pages.
Since it was only this PC with the symptom I figured it was one of the many add-ons causing the trouble. I disabled them all and sure enough the problem disappeared. Carefully re-enabling add-ons a few at a time I determined the culprit was MozCC.
A Google search led to this promising article but then I realized I already had a newer version. Checking the comments on the main MozCC page gave me the solution posted by Tyran. I quickly hacked up the version override and MozCC 1.21 works great in Firefox 2.
Paul Hutchinson's Blog 