Yup, that's definitely odd. Can you go to Global Configuration of Joomla and set Error Reporting to "Maximum". That should show an error message on the page that will help narrow things down.
Other things to check are that in the Plugin Manager, you only have the jfbcprofile type plugins enabled for extensions that you actually have installed. If you enable plugins for extensions that you don't have installed, that could cause similar problems.
Hope that helps get you started,
Alex