Windows proabably shuts the network connection when your laptop goes to sleep/standby. Plus MS updates sometimes prevent network access by changing the power saving settings on your network card to enable Windows to switch off the card to save power.
I'm on XP so I go to Network Connections, right click Local Area Connection>Properties>General tab
click Configure (next to the network card box), select power management tab . here you'll see two options: 'allow the computer to turn off this device to save power' and 'allow this device to bring the computer out of standby'.
The second tick box could be what you are after. In my case only the first one is ticked and I untick it if I have connection problems. The second tick box could be what you are after.