It is a bug in the forum module.
When you log on and stay logged in for something like and hour, you are technically logged out, but if you post again before logging in then it does not check to see if you are logged in and gets confused because you really made a post with out being an active user.
The bug will be fixed in the next update, but until then I have to go in and change the database to make it think I am the user that made the post.
bugs like this happen when you use free open source products.
You guys keep break'in it I will keep fixing it.
Jay