Honestly I don't know. It works on my MacBook running lion
Oh :/ well ill try my aforementioned thought and update the thread with results. Thanks!
UPDATE: Yes, clicking uninstall iMessage Beta (Messages > Uninstall Messages Beta), restarting, then reinstalling Messages Beta via the zip I still had on my HDD. After reinstaling, you have to go to preferences and sign into your iMessage account. If yours says inactive like mine did, click account details (under preferences) and select your location.
Good luck and happy iMessaging