You've used ob_start() on line 1151 of the plugin in the prepare_comment_field() function, which is activated with this action:
add_action(<br /> 'template_redirect',<br /> array(<br /> __CLASS__,<br /> 'prepare_comment_field'<br /> )<br /> );<br />
The problem is that there seems to be an incompatibility with this and my own plugin Crayon Syntax Highlighter. As far as I know using ob_start() needs you to call ob_end_flush() at some point according to http://php.net/manual/en/function.ob-start.php.
The result is that the page doesn't load at all. I use ob_start() for logging purposes but call ob_end_flush() soon afterwards in the same function:
crayon_log.class.php: ob_start(); var_dump($var); $buffer = trim(strip_tags(ob_get_clean()));
I've removed this and just used strval() for now to avoid the conflict.