Being the proud owner of a Surface pro 2 and it's corresponding docking station I came across the issue where the Ethernet / network adapter was not being detected.
I tried docking and undocking several times to see if this fixed the issue without success.
What worked for me was unplugging the power cord from my docking station while the Surface was still docked and then plugging it back after 10 - 20 seconds.
My network adapter was visible again and the Surface connected to the wired network without issues.
For other troubleshooting of the docking station, you can check this Microsoft website: http://www.microsoft.com/surface/en-us/support/hardware-and-drivers/troubleshoot-docking-station
Hope this helps!