Lost connection to battle.net and Your connection has been interupted

It's more of a general error, but usually occurs when there is a network problem so they are related to each other as you seem to be getting it the moment your idle connection is being closed and your game client fails to send null packets to keep the connection alive, confirming this is most likely a network issue. Unfortunately, I can't say whether it's a provider issue or an issue with the upstream your internet provider uses, but something between you and the server is causing this problem. I'll be sending you a PM with something that you can try, as services like ExitLag could sometimes temporarily solve issues like these and if this doesn't work either, then I would give your ISP a call.