I'm getting the same error with WordPress.
I've narrowed it down to when I attempt to edit a WordPress template file to include the string "exec();" and publish it using the WordPress adminsitration utility. [The actual line of code I'm concerned about is
$feed_contents = curl_exec($ch);
but simplifying the case seemed useful.]
In the WordPress forums the suggestion is to check with the host to see if mod_security is turned on (Is that the "extra security" checkbox? I did check that) and then to check with the server folks to see if it could be configured to allow this line of code.
Does that sound reasonable?