The most common reason that a blank screen is shown even if you have error reporting on is because Joomla has thrown a fatal error from which it was unable to terminate gracefully (it didn't even have time to throw errors). Usually, the source of such problems is out of memory exceptions. What this means is that some extension you are using requires more memory than you are allowed on the server, and when Joomla tries to get the memory allocated, the server kills the process and stops abruptly, showing no error. This usually happens when you are on shared hosting, and your host is limiting the amount of memory that it can use. We strongly suggest that you upgrade to a niche Joomla hosting server.