Anytime you see the message
500 Internal Server Error
That typically indicates there is a problem with the database serving TFL. All the messages are stored in a database and the software that presents the data found some kind of "fatal" problem that prevents it from working correctly. Rather than provide bad results, it displays the error message.
Depending on what DB product is being used, the administrator will perform some maintenance procedures to correct the situation. In the worst case, the staff has to reload the database from a backup copy. This can take anywhere from 10 minutes to 24 hours, depending on the size of the database.
BillCA in CA (Unfortunately)