User tab XML-RPC Error (404): Unknown error

I have Joomla 3.4.4; Moodle 2.9.2; Joomdle 1.0.2.
While sincronizing users something went wrong ... now everything seems to work fine except for users tab ( www.pallai.it/administrator/index.php?op...m_joomdle&view=users ) which gives error.
I would like to solve this problem ... may anybody help me ?
Thank You
Gian Luca

www.joomdle.com/wiki/Category:FAQ#Why_do...29:_Unknown_Error.3F

Thank you Antonio!
I got this message:
XML-RPC Error (11120199): ERRORE: numero errato di parametri della query. Parametri attesi 1, parametri ricevuti 0. | ERRORCODE: invalidqueryparam
I think it is connected to the "No jommdle users" filter in users tab.
It may be there is an user with "bad" characters?
I found the problem appears only in this case.
Anyway I am unable to solve it ... may you help me?
What should I check?

Do you mean that the error only appears when you set filter to "not joomdle users"?
I've never seen that error, so I don't know where is coming from, sorry.

I think there may be some invalid character into usernames? Where may I find not allowed ones?
Thank you
Gian

Do you mean that the error only appears when you set filter to "not joomdle users"?
If you don't set a filter, and go through all the users, you'll see all of them, so it should give an error if the problem is related to invalid chars in username.