Locking computer disconnects from network

Hey everyone,

I recently had a hard disk failure so it was replaced and was upgraded to W7 on the way, and now every time I lock and step away from the computer for a few minutes, the network disconnects (LAN, not wireless).

Most of the forums I've seen suggest toying around with the power management features; I played around with it, but it still doesn't work. Right now my laptop is always plugged in, and it's configured never to sleep, never to spin down the hard drive, and the adapter is configured to NOT "allow the computer to turn off this device to save power".

Any suggestions? This is driving me insane...
Thanks

Some technical info:
Dell Latitude E6400
Windows 7 Enterprise 32-bit, Version 6.1.7600 Build 7600
LAN adapter: Intel 82567LM Gigabit LAN, driver version 10.0.6.0

You might try this if no one has another idea.
Open the Network and sharing centre and right click the click the Local Area Connection and then properties. Click the Advanced tab and select the first option "Device sleep on disconnect" - Disable it.
I have not tested this but maybe worth a try. be prepared to reenable if it gives you any related problems.

Apparently, updating the driver fixed the problem.
Thanks though