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

Pending an update from 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

If I recall correctly Norton are expecting to release a compatible toolbar in a couple of months time, there have been a few recent posts about this problem

Firefox itself provides some similar functions to those of the Norton toolbar. The toolbar also provides an 'Identity Safe' which I understands allows you (in addition to use info on secure websites, ) to store miscellaneous info encrypted on a memory stick, something I am sure other software will do.

;-)  think I had intended to post this in another thread