I've just put together an Ivy Bridge system based around an MSI Z77A-GD65 mainboard, and things are going well except for the on board Intel 82579V network port: every so often (more frequently at high system loads), the network port will completely fail. Windows 7 reports that my cable has been disconnected, and the link lights on the port and my router go out.
Rebooting does not fix the problem, nor does simply disabling/reenabling the device in Device Manager. Device Manager actually doesn't report a problem unless I reboot, then it complains the device can't start (code 10). Swapping cables hasn't helped. The only reliable solution I've found so far is to uninstall and reinstall the driver. That restores connectivity 100% of the time, but only until the port fails again later on.
MSI Z77A-GD65 mainboard (current BIOS as of 5/4)
Win7 Pro 64 SP1 (no pending updates)
Running in BIOS mode (couldn't install in UEFI mode, but thats another problem)