I use a VPN to connect to a microsoft exchange at work. For some reason, just since this morning, it has automatically disconnected itself after around 5 minutes. The compuer seems to think it's still connected (as the icon is showing and counting away at the bottom of the screen) but I can't map to a network drive and Outlook is telling me that the connection to the exchange has been lost. Have tried a system restore but that hasn't worked.

It's not a Sky/router issue as it's working fine on my laptop.

Any ideas?