Advanced Poll Fatal Error

I'm getting the following error message when trying to login to the Advanced Poll Admin. I put in the username and password and then get this error message:

Fatal error: Call to unsupported or undefined function flock() in ../include/class_session.php on line 48

I've tried commenting out the flock lines 48-51 and then the admin page will load but if I click on any of the management icon/links I get bumped back to the login page.

Thanks!

commenting out the lines 48-51 will also disable the write operation!

// flock($fp, 2);
fwrite($fp, $config);
// flock($fp, 3);
fclose($fp);