Currently Being ModeratedJul 11, 2013 2:11 PM (in response to stephanpellegrini)
The Messages app in Mountain Lion can send iMessages if you have entered in an Apple ID.
You can also have AIM, Jabber ot Yahoo accounts as well.
The iMessages account can be set up to link with an iPhone Number and will then sync (display) the iMessages on the Mac and on the iPhone (iPads and some iPod Touch items can also be in the loop).
There is a known issue on the Mac version that if you have been using the iPhone and the Mac has been Off, when Messages is launched the Sync may be out of order.
In worst cases the new messages still being sent to you will be received Instantly and be out of order.
Restarting the app is reported by some to provide some relief to this (it is not a total answer).
Apple reported that in the OS X 10.8.4 update that had changed one items that was one possible cause to this issue.
However the app remains at version 7.0.1 so that change is somewhere else in the set up.
Few people have rush back here to say it solved it for them (most reports still say it is not effective).
I would use this iChat Feedback page
Under the hood the app is still iChat
The Version drop downs have always been a problem on this page so type your details in the Free Text area.
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.4)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously