A guarantee? Shirley you jest.

The Google Toolbar is dead for Firefox.
http://googletoolbarhelp.blogspot.com/2011/07/update-on-google-toolbar-for-firefox.html

Norton has a compatibility patch for Firefox 6.
http://community.norton.com/t5/Norton-360/Update-Available-Firefox-6-0-Compatibility-Patch/td-p/512484

You'll have to see if those other two have been updated for Firefox 6.0 yet, or not. Mozilla doesn't update stuff that they didn't create.

Its the job of Add-on Developers and External Software vendors to update their products in order to become Compatible with Firefox.

Its the job of the Mozilla QA team to assure that they don't create a non-interoperable browser; it is also their job to coordinate all interface changes to their communities of interest, including "add-ons" especially SECURITY SUPPORT packages. The better work-around is not to get on a high-horse and have Firefox updater arbitrarily disable an add-on, it is to back off of the update and notify the QC squad and the Mozilla Security team that the upgrade is an issue.

Saying that either interoperable quality or security is someone else's job is unprofessional. You think that the Mozilla management wants this mis-stated corporate practice reported to ISACA, ISSA, QAI, NIST, SEI, and ASQ-SD?? That is not an a response worthy of either ISO-9000 nor CMMI Level2.

Hi Waldorf_Mike. As has been stated, Norton have considered it their job, and have issued a compatibility update.

Never update to a new version until you're sure your old apps work with it.