That indicates that an add-on you have is not compatible, to troubleshoot this follow the procedure in this link - https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes

Hi Tony E,

Thx for your link.

I have removed the Ask Tool bar from Add-ons, after which the problem got resolved.

Hope this solution is useful to others too.

Thx/Rgds

Navi

Please click the Helpful button next to the answer that solved your Firefox support issue, when you are logged in, so this thread gets marked as Solved.