Issue in Italian Locale Rated 5 out of 5 stars
It is a problem of the Italian Locale. Delete all locales and references (in install.rdf, chrome.manifest and \chrome\locale\) leaving the en-US locale only.
This will give you access to the option panel (in english). With more investigations it should be possible to find the problem inside the italian locale files.
NOTE: the files are coded in UTF-8, so it is not a problem related to Italian accented characters.
EDIT: I found the problem. The Italian locale is referenced as "it-IT" in the chrome.manifest file, while the folder in \chrome\locale\ is simply named "it".
Rename the folder as it-IT and the option panel will work correctly.