I have a laptop user on a D600 that has recently begun haivng intermittent network issues.  She continuously gets bounched on and off the network (which happens within a second).  Here's the troubleshooting that I've done:

Installed all the latest drivers, firmware and BIOS updates

Tried swapping out docking stations, and also tried to just use the internal NIC

Swapped out network cable

Had engineer check for collision errors on switch

Swapped out ports on the patch panel

Hard coded NIC to 100/full

Set Lanman "reconnect" reg entry to highest setting

Other than that, I can't think of anything.  She's running Windows 2000 pro, and this is the second laptop she's recieved because of this.  Anyone with any ideas or suggestions?  Any help will be greatly apprciated!