Our team (and a lot others) had this problem too. FIRST acknowledged it in Update 08, and released the update to the FRC Radio Configuration in Update 10.
I would download the new FRC Radio Configuration utility (
HERE) and re-flash the new firmware on your radio and see if that works.
If that doesn't end up working: we moved the ethernet connection to the other port (the port closest to the power connector), and that fixed it (according to
Team Update 08)