WNDR4500v3 router ethernet bug in firmware 1.0.0.56

I've noticed a bug that affects the router's ethernet ports with the latest 1.0.0.56 firmware - Gmail and some other websites take a long time to load on devices connected to the router via ethernet. This does not happen when using the wifi connection. Rolling back firmware to 1.0.0.54 fixes the problem. Any ideas?