I'm having the same problem but with afp and can now reliably repeat the creation of the 'wellknown' ticket.
On the client
1. Delete all identities in Ticket views
2. Go to finder and click on my server from a local folder - this will generate the '@WELLKNOWN:COM.APPLE.LKDC' ticket every time.
3. Finder hangs for a few moments and then shows the shared directories (I'm guessing not using kerberos)
I think the issue with afp is to do with using .local rather than the full qualified domain name that the other services are using and this might be a similar problem with iChat.
I was having problems with the mail server and clients authenticating to it but fixed that by clearing out the local KDC (LKDC) on the Client using
1. sudo rm -rf /var/db/krb5kdc
2. sudo rm -rf /etc/krb5.keytab
3. sudo rm -rf /Library/Preferences/edu.mit.Kerberos
4. Bind the Client to the Server again.
I have the server running Mail, Calendar and Contact, and watching the ticket viewer Contacts is very reliable at creating the correct tickets when I start it.
Have you tried setting the correct ticket as 'default' using the button in ticket viewer or deleting all the identities and adding the correct ticket directly in ticket viewer then making it default? This might help with the reset on re-login.
For reference both the client and server are running 10.8 and were upgraded from 10.7.4.
Hope this helps and if I find anything else useful out I'll post it