After I click Change Identity, and type in a new username, I have to type in the 'Security Check; Password' box. But after I done that and clicked Change Username, it says 'Your password did not match!' Help, did I do anything incorrectly?

It means that you didn't type in the password that you use to log into your Subeta account.

Oh! I just changed my password and now it works. Thank you anyway. ^_^ Could someone please lock this topic? :P

Locking this right now :)