Probleme instalare Add-on-uri Firefox

In caz ca aveti probleme la instalarea de Add-on-uri in Firefox, si primiti o eroare de genul :

Firefox could not install the file at...
because unexpected installation error
Review the error console log for more details.

Atunci tot ceea ce trebuie sa faceti e sa stergeti aceste 3 fisiere: extensions.ini, extensions.cache si extensions.rdf din profilul Firefox

Locatie Profil Firefox :
Windows XP : C:\Documents and Settings\[User Name]\Application Data\Mozilla\Firefox\Profiles\
Windows Vista : C:\users\[User Name]\AppData\Roaming\Mozilla\Firefox\Profiles\