When you Install Message you need to restart the computer to put all the bits in place.
Then when you start the app it requires you enter an Apple ID.
This Apple ID should have any email linked to it Verified.
If you were using iChat before then your Buddy lists with AIM, Jabber or Yahoo are still there (See Window Menu)
However they are linked in to one Display list (See Preferences > General Section to Unlink).
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Lion 10.7.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images." No, Seriously