Hi,
Yes in my Pic the one above Bonjour is the iMessages one that is only present in Messages.
This is Apple's own Messaging service that works with iOS devices and has been added into iChat in Mountain Lion causing the Name change for the App.
The icons for each type of account are slightly larger and a little different from earlier versions
AIM Accounts tended to get the running yellow man.
All Jabber Accounts including Google got the Lightbulb icon.
Bonjour has always had the three pointed star like icon since the Accounts were in a list form from iChat 3
iChat 3 Pic
I did not buy a computer that would run Lion and Mountain Lion until quite late and did not stay with Lion for very long.
I made the mistake of not cloning the Lion boot that came with this iMac to still be able to look at things.
So I am without iChat 6 and a chance to see the Accounts pane in the preferences.
However the process for adding accounts that have Buddy Lists (as in iChat) is the same in Messages.
You access the Preferences> Accounts and use the + icon at the bottom of the list.
The top item in the new pane is a drop down.
It gives you the AIM and AIM Valid options that were current at the time (MobileMe and historical @mac.com names).
Below the line are the Jabber options including Googletalk (this makes sure the right server name is used).
iChat 6 and it's updates through the life of Lion and it's updates should work for the @icloud.com name.
Can you confirm for me that the @icloud.com account is trying to login to the api.oscar.aol.com server ?
Or it is using the older login.oscar.aol.com one ? (this one might have a leading "s" if using SSL to login)
If using the api server it should be using port 443
The older one that was used at least until iChat 5 can be logged in to port 5190 by default although port 443 works as well.
If it is the older server try changing the port to 443.
It is late where I am and it may be a while before I catch up with your next reply.
10:35 PM Saturday; May 25, 2013
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.3)
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