Postie plugin issues

I’ve had postie running successfully on older versions of WordPress with no issues along with the associated cron job. When upgrading to the latest version though (WordPress and postie), I can’t seem to get postie to work. I can activate the plugin successfully and view the postie option settings, but that’s where it all ends. When I try to run test config under the options to check my settings, I continually get a 500 server error in the source code. Check it here: http://www.readyaboutllc.com/wp-content/plugins/postie/config_handler.php

View the source of this blank page and you’ll see what I mean e.g. <!– SHTML Wrapper – 500 Server Error –>. Could this be a permissions related issue on the postie directory? I’m really stumped so any help is greatly appreciated.