"Remove Ad and Flash blocking extensions before installing a new version of Firefox or Mozilla

When you install Mozilla Firefox 0.9 (or later) or Mozilla 1.7 (or later), you may experience problems viewing Macromedia Flash content if you had a previous version of Firefox or Mozilla and extensions installed to block ads or Flash. Examples include AdBlock and Flash Click To View.

Before installing a new version of Firefox or Mozilla, you should uninstall your previous version, and remove the chrome and extensions folders from your profile - but back up userChrome.css and userContent.css first if you use them.

Dedicated Flash blocking extensions will need to be updated to work with new Firefox and Mozilla releases before you can use them, as the Flash blocking code tends to break between Mozilla releases.

This problem is also caused by the Flash filtering code in old releases of AdBlock, and does not appear to require the user to enable it. Updating AdBlock to version 0.52 or later should solve this problem."