Can't get an image on my HDTV...

I got a mini-DVI to HDMI adapter and an HDMI cord that connects to my tv. When I plugged it in my Macbook Pro flashed blue but I got no image on any of the inputs on my tv. I also checked the system preferences to detect displays but got nothing to show up there.

How can I get my tv to work as a monitor? Mirror or dual screens.. I'd be happy either way.