Hi diveshsareen

see : Command line arguments - For Linux and Mac OS X users

try cor-el reply in the next link : https://support.mozilla.org/en-US/questions/923286

thank you

You get that message if the extension needs to be unpacked to run properly because it want to make changes or save data in its extension folder.
The normal way is to copy the extensions XPI file to its extensions folder without unpacking all files.

• https://developer.mozilla.org/En/Updating_extensions_for_Firefox_4.0#XPI_unpacking

Which extension(s) give you that error message?

Hi Guys, I am having issue installing firebug and web developer. Is there an easy fix / step by step guide or video I can refer to please ?? Thanks.

Try to set the Boolean pref extensions.alwaysUnpack to true on the about:config page.

• http://kb.mozillazine.org/about:config

Hey,

I'm having the exact same issue, except I'm on OSX 10.8.2 and FF 16.0.1.

I can't install any extensions. If I try via Tools -> Add Ons, I get the error "There was an error installing <extension-name>". If I try via the addons.mozilla.org site I get the "can't modify file" error msg.

I have changed extensions.alwaysUnpack to TRUE, but there is no change.

Any help would be greatly appreciated.

You can try resetting the account by using the link :

http://support.mozilla.org/en-US/kb/reset-firefox-easily-fix-most-problems

Hope this helps.

I mean try resetting firefox as this resolved the issue for me.

That worked perfect, I now have Firebug.

Thank you