Me also.
What I have discoverd is when you get the internal server error, this is AFTER your message has already been sent, PM, post whatever.
That is why you will see double posts, people thinking it didnt go through.
What I suspect is happening is after the system sends the message or makes the post, it is choking trying to return you to where you were.
So for everyone, until this gets resolved, just send your PM's and check the box that has a copy sent to your sent folder. if you receive the internal server error, just go badck to the thread and more than likey your post will be there. dont try to refresh, or go back and post again.