iMessage - email already in use

I (along with many others) are having problems setting up Message/iMessage. No matter which device I try (iPhone, iPad or iMac) I get the same response that the email address, my @me account is being used by another AppleID, but as far as I can see it is not.

I have two Apple ID's, one using my @gmail.com email address for my iTunes purchases, iTunes Match, etc and my @me.com account for iCloud. It is the @me.com account I want to use for iMessages, but I constantly get the same error and even get the same message with FaceTime.

Has anyone successfully managed to use and iCloud (@me.com) account in Messages across multiple devices? or is it a case of waiting for IOS to come out, although this may cause more issues.

Cheers

Chris