I am using Kunena version 1.6.4 for Jommla 1.5.22. I have also Community Builder installed (version 1.4 ). So I have integrated Kunena to Community builder in the Kunena configuration.

When a Guest is viewing then no user avator is appearing in the Kunena forum, which is connected to Community Builder for user profile. However, when a user logins then avator of all the users start appearing.
Similar problem happened to me using Blogs (EasyBlog). After investigation on my site, we found that Community Builder API to get the user avator is not working.
It may be similar problem here. Please help.