WD TV Plus will not accept DNS address

I have a WD TV PLUS about 3 years old. It has the latest firmware but when the DNS address is entered the DNS line goes blank, however the entered address still shows when checking the network settings. Even with the correct dns enetered the unit stillfais the network communication check. After powering downand restarting the unit all of the network information is lost. Any body have any ideas.

Back again. Reloaded earlier version and all works again.