Adam,
I personally have never seen it. We have a small community with a max of 20 users chatting at any one time. There are about 5 users who cannot add the avatars.
In a related note, I also have several users getting error 12029 and getting booted out of the chat room. This again has not happened to me but it is evident when it happens.
We have a domain license for the Chat software that is integrated with Community Server.
Any help to get these users off my back would be appreciated.