I am also having a problem where Send/ receive says "no addresses" and my phone number is checked and grey. I have logged out even reset my phone. iMessage still isn't working. Very frustrated!!!
Well i guess i fixed it
1)turn off imessage
2) go to contacts and create your own contact with only your own number, no email
3)go to settings-phone-my number, and type in your number without the +61
4)go to settings-general-date and time. make sure the 'set automatically' is on
5)go to settings-mail,contacts,calenders, then in my info, select your own contact.
6)forget your wifi network and then join again
7) turn on imessage.
it should work. it worked for me. step 3-6 doesnt necessarily have to be in that order.