Hi,
Mountain Lion is the latest version of the software
When it was released the version number was OS X 10.8
Since then there have been two up dates (10.8.1. and 10.8.2)
Your original post says OS X 10.8.2
iChat and now Messages get occasional Updates along with the OS Updates.
Messages in Mountain Lion has had one update at the OS 10.8.2 update to make it version 7.0.1
You have the latest version.
IF you have an Apple ID listed in the Messages > Preferences > Accounts and and AIM Screen Name then you should be able to send IMs to Buddies.
To be sure I would display the Buddies List (Window Menu > Buddies or CMD + 1)
Your Buddies that you added when you used iChat will be shown there.
You can of course click the "New Message" icon in the Messages window then the Blue + icon and choose Buddies then a specific Buddy.
That will get you Text Chatting.
At this point the Messages window Blue + icon changes to a Video icon
This is used to call the Buddy you are chatting with.
Alternatively the Buddy list will display the same Green Video and Audio icons that were seen in iChat and you can call a Buddy without starting a Text chat.
IF you are not getting Incoming Invites for Video chats then check port 5678 is open in your Modem or router.
Both the Mac Firewall and the router will allow outgoing data which is probably why your Buddies are seeing the invite.
You have to allow the incoming Data.
Also Check the Mac Firewall (System Preferences > Security & Privacy > Firewall > Unlock pane > Firewall Options - in here the Allow Signed Software should be ticked and Messages should be in the list. )
7:43 PM Tuesday; November 13, 2012
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
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
Message was edited by: Ralph Johns (UK)