Error message 'Only variables should be assigned by reference' - Joomla! Forum - community, help and support

hi, installed bannersmanager , ads working of main menu pages show error message above banner:
notice: variables should assigned reference in /home/sites/mysite.co.uk/public_html/includes/joomla.php on line 4270

i using standard template, opensef , various other components pages affected not same types (static link, blog, content item, etc)

this section joomla.php (line marked asterisk):

/**
* same trigger returns first event and
* allows variable argument list
* @param string event name
* @return array result of first function call
*/
function call( $event ) {
$dounpublished=false;

* $args =& func_get_args();
array_shift( $args );

if (isset( $this->_events[$event] )) {
foreach ($this->_events[$event] $func) {
if (function_exists( $func[0] )) {
if ($this->_bots[$func[1]]->published) {
return call_user_func_array( $func[0], $args );
}
}
}
}
return null;
}
}

at moment i've removed bannersmanager module affected pages , displayed original banner module there instead no errors, means can't apply either of them default.

can explain or suggest fix please?

thanks help