When trying to set up Apple ID password for Messages on my iPad Mini (for the first time), it shows my email address, but won't allow me to use the SAME password I use for all my other Apple products (browser, iPhone 5, iTunes, etc). Is there such a thing as MULTIPLE Apple passwords? I can purchase songs on iTunes using my existing password. Shut down Mini, restarted, and tried it several times but keep getting same 'incorrect' response. Any ideas?