Empty delimiter error.

Everything seems to be working fine however I'm still getting an error at the top of the arcade in my forum

Warning: strpos() [function.strpos]: Empty delimiter in [path]/arcade.php on line 3508

when I check it out in my php that line reads
if ((strpos($referer,"arcade.php") > 0) && (strpos($referer,$vboptions[bburl]) > 0))

can anyone shed some light on this problem???