I have the same Issue. The index.php?option=com_comprofiler&task=userslist&Itemid=184 Page works fine in IE but does show a blank page on firefox. I also tried to turn on the Joomla debug mode but the page is still blank (also no source).
Have you referred to the FAQ? Does it work with the default Joomla template? What versions CB, Joomla, PHP? Have you checked your server error log? Please see the Help Us Help You in my signature.