Unable to install themes or extensions in Firefox

After the last firefox update is installed, all my extensions are stop working. I can't install again from add-on. When I install the extension, it shows Unexpected installation error -203 above pictures. I google it and found this address :

http://kb.mozillazine.org/Unable_to_install_themes_or_extensions_-_Firefox#Unexpected_installation_error_-203

and I got the solution

1. Open run box > type %AppData% and click open
2. Browse to Mozilla\Firefox\Profiles
3. Delete these 3 files:
extensions.ini
extensions.cache
extensions.rdf

4. Close Firefox and install the extensions

Now its work.. :)