Microsoft Communicator Error - The current machine is not in the list of internal servers - 0xC3E92047

I recently upgraded a number of users' sign-in email addresses on LCS to a different domain name (this wasn't actually another AD domain, just a different sign-in email address). Upon restarting the LCS service I got the following error:

'The current machine is not in the list of internal servers. This may cause the server to have interoperability issues.'

LCS had been working fine up until I changed approx 60+ users' sign-in names from @domain1.com to @domain2.com. I shut both the LCS Service and the Archiving Service down before doing
this, but on trying to restart the service I got the error above. I had the correct domains listed in the forest, so domain1.com and domain2.com were there. I tested a few users being changed over to this new sign-in name before starting and all worked fine.

The microsoft knowledge base article for this error (http://support.microsoft.com/kb/896557/ ) says to check the
dns suffix on the server. In my case this is corrcect - the server itself is running fine. DNS resolved to the correct addresses, the server could ping the domain controllers and had full access to them - no firewalls in between. I couldn't have attempted to change the dns suffix of the server (even though it is correct) as it was a Certificate Authority and hosted many other applications, which all were working fine.

I tried running dcdiag/netdiag (i was getting nowhere, so wondered if DNS was having issues etc) but all come back completely fine.

In the end, it turned out for whatever reason I had to Deactivate then Reactive the LCS server! All worked fine after that!

I've no idea why this happened or what made the problem occur - i'd tested migrating a few users to the new sign-in address to ensue it worked, before changing everyone's, but either way the problem occured. I'm guessing a bug with LCS?