Everytime I try to connect my Laptop to my 37 inch tv it says "invalid mode"?

So i have a Dell Studio 1558 Laptop. It's capable with HDMI and so is my TV. My Tv is a Proton 37 inch 720p tv. I try connecting my laptop to it through HDMI but it comes up with "invalid mode" and then my laptop goes black until I take out the HDMI cord out of my laptop. I want to watch a movie on my tv and the file is on my laptop. Someone help me please!