problem login form

-- url of the page with the problem -- : www.mbstampa.it/mbstampa
-- HikaShop version -- : 2.2.3
-- Joomla version -- : 3.2
-- PHP version -- : x.x.x
-- Browser(s) name and version -- : XXXXX x.x.x
-- Error-message(debug-mod must be tuned on) -- : Error_message

Hi, I have a problem with the login form
when a customer registers gets a message saying that everything is ok
but when he puts the username and password a message comes saying that the
user or password is incorrect or there is not yet an account

thanks
mark

thank youuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu