Mark! fear not! you are simply just signed into iMessages now, by default, and I assume you had performed a clean install?
In any case, if you want to screen share with your apple id still, you will simply have to use your apple id you used before to sign into AIM servers. this will allow you to see your old buddy list again, exactly how you had it, and most importantly, talk with your parents!
Messages>settings>accounts>add a new AIM account but sign in like you would iCloud or this forum. (trust me, it'll work).
Nice try, Monster, but no go.
It was an upgrade-in-place over Lion, fully updated.
This was a problem when we tried out the iMessage beta last year too - and I went back to the plain vanilla iChat.
In the Messages Preferences-->Accounts window, I am logged in to both my Messages account and the AIM / iChat account.
I do have a buddy list. I am able to use it to initiate text chats. But initiating a video or screen sharing attempt results in no incoming chat request for the person on the old version of iChat.
I can successfully do audio / video / screen sharing chats with a friend using Snow Leopard & iChat.
But that old G4, with it's ancient iChat, just doesn't speak the same language, it seems...
Here you can see the picture.
Yes, I'm able to do screen sharing, plus I'm not the only one with this.
And, Mountain Lion and Messages are innocents. : (
It's happening whit my other mac between ichat and Lion.
It seems you are the Original Poster have different problems.
I have three computers here
1) an iMac running Mountain Lion and Messages ver 7
2) A MacBook Pro running Snow Leopard and iChat 5
3) A G4/1ghz Dual Processor tower running Leopard and iChat 4
I and Screen Share, Video chat and Audio chat between all of them.
I tired Bonjour and AIM names to do this.
It did take several attempts before the iMac seemed to "remember" it had done this in Lion and iChat 6 and Messages beta.
On all computers in iChat or Messages Menu > Preferences > Video Section I Have the Bandwidth set to 500kbps.
This helps, if like me, you have someone using a X Box 360 On-line and using varying amounts of bandwidth or your ISP service speeds vary or one of you is much faster over the internet than the other.
With the Video chats and the "Buddy List" I would go one stage further if you have several account logged in.
Go to the Messages Menu > Preference > General Section and untick the option that links the Accounts Into One Buddy list.
This may take up more desktop screen area but you can be sure of using the "right" name if the person has more that one ID or Screen Name in their Address book card.
It also makes it easier to check the Security Setting in any AIM Account that might be Blocking Buddies.
Get your Parent to start the chat.
Apple may have reduced the Testing Accounts to one at present but can you Video with any of table 1 ?
iChat 6 and Messages log in to AIM on the API servers using port 443
This tends to mean you can login as this port is below the 1024 threshold
If you set up Port Forwarding before with iChat and you have a different IP now (sometimes happens when Upgrading) your Router settings may not be pointing to your computer.
I would use UPnP (or Port Mapping Protocol in a Base Station) if you have it.
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Lion 10.7.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images." No, Seriously
Thanks for the detailed response. I'm loathe to go messing with settings that have worked for the past year... the one thing that has changed in this scenario is me - I've gone to Messages on 10.8 from iChat on 10.7.
I doubt many other people are still trying to do video chats with someone on iChat 3 - but that's the upper limit on my folks' old computer. It's at the maximum OS version now, and I'm some 1500km away from them.
They can't begin the video chat because their computer has no iChat camera... but when I initiate, they are able to see our video stream (and hence, their new grandson).
I'll see if I can walk 'em through checking the bandwidth cap - mine is usually set to unlimited, as I have a fast cable connection, as do they.
Note that *I* can do video with other people on computers and iChat apps newer than my folks' machine... it's only with them that this occurs.... and of course, it's the most important of the people with whom I chat.
Should I find a solution, will post it.