WD TV Live: 100 Mit/s via LAN?

I have a 100 mit/s internet connection which is proven by a speedtest via Win7. If I connect the WD TV Live Media Player via LAN to my router, the maxdome speedtest shows me only 30 Mbit/s and also the speed is very unstable so there is always a high change in the speed (between 5 and 35 Mbit/s). This leeds to disconnection by watching online stream on maxdome (German video library). Is the WD not able to have a 100 Mbit/s connection?

I don’t think it’ll go beyond 40.