I had one from them on test. I used exactly the same modem as you, and had exactly the same problem. Several calls to Belkin support served to tell me two things:-
1. Their telephone support is superb
2. The fault isn't with the router - they even sent me a second one to prove the point.
In the end I wanted to hurl the D-Link modem as far as I could see it, and I ran out of time and patience, so I abandoned the whole idea.
None of that helps you much, but sometimes it's good to know that you're not alone, and not stupid.