Network randomly disconnects and suggests there is no cable plugged in.

[FZE]

Just built my new computer, all is going smoothly except for my networking. The card is a Realtek PCIe GBE family controller, onboard an MSI P67A-G45, and I'm running Windows 7 32-bit edition. The issue I'm having is that on every boot, the Windows networking tool tells me I'm not connected to a network, and that no ethernet cable is plugged in. If I check the board itself, the two lights on the NIC are off, but if I unplug the cable and plug it back in, they light up, and Windows is then able to connect to my network. The cable isn't being moved, and clicks into place, so I'm fairly certain it isn't being physically disconnected, and I've installed up-to-date drivers for the card. I don't know if the issue is the card itself or Windows is having trouble with it. Any thoughts on what might be happening?