HI,
Lets back up and check we are looking in the same place and using similar language to describe things.
In the Message Menu use the Accounts option.
This will list all your "Accounts" (which may be iMessages and Bonjour).
Ticked ones are Logged in or active.
1) Is iMessages logged in ? (Ticked)
In Messages Menu > Preferences > Accounts you seem to be describing that there is an iMessages account.
2) Does it have the "Enable this account" box ticked ?
Hopefully the answers to 1) and 2) are both yes.
This bit then confuses me:-
messages tab login is greyed out
The iMessages account pane has no tab.
It has some buttons (Sign Out, Details) that lead elsewhere and it has a Drop down (if you have more Send "aliases") as the bottom of the Pane.
The Main Messages window - which is an interface to start a Chat also has nothing I would call a tab.
However in this window most thinsg are grey anyway.
The icon that looks like a box with a pencil over it that starts a New Message is grey but is active.
You can just Type Names at the "To" Field and it will search the Contacts app for both Buddy Names/ID and "Real Names".
The "To" of this field is also grey but active.
If I type "Ralph" into the "To" field I get about 15 or so options
Some are iMessages registered details such as the iPhone number in my Addres Card.
Some are AIM (And AIM Valid) registered Names from AIM and Apple IDs.
There are Jabber IDs (GoogleTalk is normally listed separately)
and so on.
Some of them are listed against the Address Cards I have fro my two other computers but have similar Cards set up
Some of the info is not linked to any Address card.
In the No Name bit are two listed as being Jabber then GoogleTalk.
In fact the first is a Gmail email and should be GoogleTalk. The second is a different Jabber name and should not be listed as GoogleTalk.
One higher up is listed as both AIM and Yahoo. (it seems to strip the @yahoo bit out)
It even thinks a Land line number is an iMessage possible
Basically the Account naming at this point does not seem consistent and you may get something labelled as "Jabber" when it is not.
Messages can join (with different Screen Names and IDs) the AIM service, The Jabber service (which includes Gmail GoogleTalk IDs and Facebook IDs) Yahoo and of course Apple's iMessages service.
Apple IDs used in the iMessages account that were issued by iCloud (@me.com and @icloud.com endings) can also be used as AIM valid Screen Names.
If your Apple ID is a GoogleMail ID it can also be uses as a Jabber valid ID with some set up at the Google account settings (Enable Talk)
10:54 PM Thursday; February 21, 2013
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