Shoutbox

I think I know what causes the problem as this only happens after the window has been open for a long time (i get it too)

When you open a conversation with somebody Microsoft servers start a "session" between you and the person you are talking to. After a certain amount of time (I'm not sure if its idle time or not) Microsoft will end this "session" to save on bandwidth etc. Obviously, you can still talk but they cut down on some things like the bar being show. Note: The file Does still send.

The best thing to do here is to close and re-open the window and send again... or just let it send as is.