The slowness may be caused by add-ons, too, so you might want to try turning them all off and trying it out. If that works better, then turn them on one-by-one until you identify one that cause the sluggishness.

You can of course roll back to v3, though you forfeit some security, stability, and rendering improvements.

Previous versions are available here: http://releases.mozilla.org/pub/mozilla.org/firefox/releases/

You may also wish to back up your profile for safekeeping prior to rolling back: http://support.mozilla.com/en-US/kb/Profiles

If you roll back, you will want to change your update regime to make sure you won't automatically update against your wishes.

Your solution eliminated the problem immediately. I can not tell you how much time I spent tracking this problem down and you offered a solution that worked like magic. Many thanks to you and to the Forum.

Budd Lehman