I saw this message in my WP Engine Apache/PHP error logs:
[Mon Dec 03 18:30:54 2012] [error] [client 173.2...1..1..] PHP Fatal error: Call to undefined function setup_pagelines_template() in /.../wp-content/themes/pagelines/index.php on line 50
This was with PageLines v2.3.5. I upgraded to v2.3.7 and typed in that URL myself and got the same 500 error (not a pretty one).
In case it helps/matters, I am using a child theme.