If any document remains opened for some time (example 10 mins or more) in edit mode and then tried to save after that then save is discarded and document is just refreshing
I guess you may have hit a "session timeout".
What I will suggest that you do is to set a long application timeout and a short session timeout - and use a "keep alive" custom control to make sure that the session will not time out while you are editing it.
I have tried to explain some of these features in a blog article that may give you a better overview ;-)
/John