[Thu May 12 03:14:41.562083 2016] [core:error] [pid 25726] [client 68.71.XXX.XXX:44611] End of script output before headers: manage.php
[Thu May 12 03:14:41.697026 2016] [:error] [pid 26855] [client 84.91.XXX.XXX:60222] SoftException in Application.cpp:256: File “/home/rocker/public_html/system/manage.php” is writeable by group

I had to set the file to 755.

As seen on http://stackoverflow.com/questions/17583341/error-500-premature-end-of-script-headers