There are some limitations of Plus! for non-Skype friends, which are contacts using other networks such Windows Live Messenger.
Unfortunately, chat logging does not work for non-Skype friends.
However, all Messenger Plus! features are available for msn contacts connected to Skype using their Live account.
To help you, provide a screenshot of your contact list, use paint to erase their names
. Also highlight your contacts for which logging is not working.