Error codeigniter / Common.php and database / DB.php

To try to open my DBO site but is giving this error can anyone help?

  

A PHP Error was encountered

     

Severity: Notice

     

Message: Only variables should be passed by reference

     

Filename: codeigniter / Common.php

     

Line Number: 148

     

A PHP Error was encountered

     

Severity: Notice

     

Message: Only variables should be passed by reference

     

Filename: database / DB.php   Line Number: 133

Common: line 148

$objects[$class] =& instantiate_class(new $name());
return $objects[$class];

DB: line 133

$DB =& instantiate_class(new $driver($params));