Symantec need to update their Firefox add-ons so that they are compatible with Firefox 4. They have indicated that for Norton 360 they plan to release an update to Norton 360 to support Firefox 4 in early May - http://us.norton.com/support/kb/web_view.jsp?wv_type=public_web&docurl=20100720113635EN&ln=en_US

I do not know about the time scale for updates for other Norton products. Pending the update by Symantec, if you want to use the Norton add-ons you will need to downgrade to Firefox 3.6.

To downgrade to Firefox 3.6 first uninstall Firefox 4, but do not select the option to "Remove my Firefox personal data". If you select that option it will delete your bookmarks, passwords and other user data.

You can then install the latest version of Firefox 3.6 available from http://www.mozilla.com/en-US/firefox/all-older.html - it will automatically use your current bookmarks, passwords etc.

To avoid possible problems with downgrading, I recommend going to your profile folder and deleting the following files if they exist - extensions.cache, extensions.rdf, extensions.ini, extensions.sqlite and localstore.rdf. Deleting these files will force Firefox to rebuild the list of installed extensions, checking their compatibility, and reset toolbar customizations.

For details of how to find your profile folder see https://support.mozilla.com/kb/Profiles

Thank you TonyE. You addressed all of my concerns. I was getting ready to uninstall Firefox 4 and load 3.6 but didn't know how to do this without losing bookmarks, etc.

I expect Norton 360 will come through with updates soon but in the meantime, I will follow your excellent instructions. -Stinger

OMG, This was driving me crazy. I upgraded to Firefox 4.0 and my Norton toolbar wasn't working - so all my stored log-ins under Identify Safe weren't available. I looked for a solution for over a week until I found this solution and now it's working perfectly! Thanks so much!