Messages won't work with iMessage after Mountain Lion install
I previously had Messages Beta installed on both my Macbook and iMac and they worked great. Now I upgraded to Mountain Lion and Messages works fine on my iMac, but not on my Macbook. It defaults to Bonjour and when I enter the Apple ID info I get a message "Your Apple ID "xxxxxxxx@xxxxx.com" can't be used to set up iMessage at this time.", and it says to contact customer support. What is causing this and does anyone know how to fix it?
MacBook (13-inch Aluminum Late 2008), OS X Mountain Lion