This has been seen before. Take a look at this thread:
EX58-UD5 Problem
Mine is fixed - either by updating bios and/or using different drivers. I know - it doesn't seem like it could be drivers. My theory is that the drivers do something illegal to the hardware leaving the lans locked up. Anyway, use the latest bios and, for Windows,
don't let Windows install the lan drivers dated October. Download them from Realtek.