Start Firefox in Use Troubleshoot Mode in Firefox to check if one of the add-ons is causing the problem (switch to the DEFAULT theme: Tools > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.

See:

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

I disabled the "ZoneAlram Toolbar" in Aurora 6.0a2 (FF 6) and that error pop-up ceased.

Other people have had to disable different Add-ons to to fix the problem (Google for suggestions). It is unfortunate that the pop-up does not indicate which Add-on is causing it to pop-up.

I was having problems with Avast's WebRep plugin not being compatible with FF 6.0. I downloaded the Compatibility Reporter and this error occurred.

I reinstalled ZoneAlarm, problem gone.

Thank you bernie_PPL, reinstalling ZoneAlarm did it for me. Colin