Some server environments by default do not have PHP error reporting turned on. If you have cPanel access or access to the PHP config on the server then you can switch the value and turn error reporting on, however this is not always practical/possible. Therefore here is a quick and easy way to turn error reporting on and off.
Simply add the following code into the top of index.php in your Magento installation:
This will then quickly turn on error reporting, which will ofter allow you to outline a PHP bug.