Why does the tick in 'work offline' keep coming back

Because your browser thinks that it is not connected to the Internet. What type of connection are you using? Broadband, dialup.. Do you have broadband now but previously used dialup? If so, and your primary connection type is set in your browser to use dialup, then it will think it is not connected.

In your browser, go to Tools, Internet Options.. and Connections. Set you browser to Never dial a connection if you no longer use dialup.