I just sent my application but is said the username was taken and to go back and try another. When I did it said that the email address was already used in an application. What should I do?
The join requests are currently clear. Check your e-mail to see if you got a response, and if not you should be able to try again. I think the system just confuses itself sometimes if it hiccups.
Its also possible you clicked the button twice, so it went through but rejected the second one since you had already gone through. As Hal said check your email to be sure.