Error script...

Hi,i like sef free version,but not work,show me this eroor.
Fatal error: Call to undefined method AcesefURI::bas() in /var/www/domain/data/www/domain.ro/administrator/components/com_acesef/library/plugin.php on line 94
Call Stack
#    Time    Memory    Function    Location
1    0.0003    76644    {main}( )    ../index.php:0
2    0.3783    9585724    JApplication->triggerEvent( )    ../index.php:72
3    0.3783    9585724    JDispatcher->trigger( )    ../application.php:500
4    0.3783    9585724    JEvent->update( )    ../dispatcher.php:170
5    0.3783    9585724    call_user_func_array ( )    ../event.php:67
6    0.3783    9585724    plgSystemAcesef->onAfterDispatch( )    ../event.php:0
7    0.3786    9585724    AcesefPlugin->onAfterDispatch( )    ../acesef.php:70
Hi,i like sef free version,but not work,show me this eroor
What can i do?