[Add-on] could not be installed because firefox cannot modify the needed file
I've tried both Zotero & Firefox forums with no success:
Zotero could not be installed because Firefox cannot modify the needed file.
I've deleted my cache, restarted firefox and computer, tried in various versions of Firefox (currently 8.0 which the add-on store says is compatible). I'm running brand new Mac with Windows for Mac 2011, have tried downloading in Safari & dropping into Firefox, from the Firefox add-ons and directly from the site. The add-ons says - unable to install & both the other methods list the above error (cannot modify the needed file).
Thanks in advance.