JCal Pro Breaks the Template
Each JCal pro extension (and our calendarwall) make a call to include JCal file 'components/com_jcalpro/config.inc.php' to get config parms...
on line 184 there's a "ob_start()";" call, which breaks the Joomla buffer handling, therefore breaking HTML rendering.
Commenting this line seems to do the trick to get a proper page.
replace line 184 with
// // Start buffering //ob_start();