Samsung Series 3 laptop does not detect some ethernet cables?

I have a Samsung Series 3 NP300E5A-AO4CA laptop. I recently bought a 30 m length of ethernet cable (Cat 5e Enhanced High Speed Network Crossover Cable). One end connects directly to the router and the other to the laptop. I've tried different ports on the router, extending the coil and swapping which end connects to the laptop but nothing works. I am running Win 7 with the Realtek PCIe GBE Family Controller (2012) driver.

I know the cable works because it works on my desktop PC.

I know the laptop's ethernet port works because other shorter cables can connect to the internet.

I've had this problem before (tried 2 other long cables that would not work).

Any help would be greatly appreciated.