There are two ways to make this work for you. The first way is to make sure, when you log on, that you check the little box next to your username that says "Remember Me". This will keep you logged into PC until you specifically log out.
The other option, which is good to use regardless of checking the Remember Me box is to type your reply in notepad or office and copy and paste it to the message box. That way, if something happens with the connection outside of PC you still have your post on your computer and you won't loose it
Hope that is helpful to you!

sabby