error در ورود به بخش مدیریت سایت

[minooamin]

salam
khaste nabashid
man hengami ke mikham varede modiriate site besham
vaghti user va password ro vared mikonamo rooye dokmeye vorood click mikonam in payam ro mide:
Fatal error: Call to undefined method stdClass:: onAuthenticate() in /home/abataz/public_html/libraries/joomla/user/authentication.php on line 121
nemitoonam vared besham
mamnoon misham raynamayim konid