hello strowien, can you try to replicate this behaviour when you launch firefox in safe mode once?

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

I had the same issue; does not happen in safe mode.

It is caused by Firebug addon.

To clarify, this happens if you have the Firebug 1.10.6 addon enabled. You can fix it by updating to Firebug version 1.11.2.

Here's how: Go to your Add-ons Manager, right click on the Firebug add-on and select "Find Updates."

Hope that helps.

Thanks guys, seems sorted after updating FireBug. A thought: now that the cause is known, how about automatic checking for FireBug version during FireFox upgrade to 20.0.1, and a msg where necessary?

It is always your responsibility to update your extensions to get the latest bug fixes.

Is updating extensions set to do this automatically (Tools > Add-ons > Extensions: Tools for all add-ons)?

I'm having the same issue on Firebug 1.11.3....The "more robust" right click menu does return when I disable the extension. Would you recommend downgrading Firebug to 1.11.2? Hate to have to turn off Firebug "except when I'm working" but either option seems to have both pros/cons.

This behavior happens on both PC and Mac (although the above information was tested on my PC - I'll have to check the Mac later and see if Firebug is doing the same thing there. I believe I have the most recent Firebug there, too)

The PC is on Firefox 20.0.1, Mac should be as well.

Thanks

Hi amergin, see stickersticker's answer (4/12/13 11:00 AM) which solved my problem.

It still annoys me somewhat that there is still no note anywhere near the dfownlad link(s) that updating FireBug is essential when updating FireFox.

Mais c'est la vie . . .

The Solution is here...i tired it out successfully

https://addons.mozilla.org/en-US/firefox/addon/menu-editor/