2009 MBP doesn't work with Mini-DisplayPort to HDMI

[StuBeck]

Last fall I bought a 6 FT mini displayport to hdmi port from monoprice for my 37" Panasonic HDTV. It barely worked (it worked once, after pressing it in 5 times), but I wasn't gaming much so didn't need it. Monoprice was not very useful with getting a replacement. Since then I have bought a 46" Samsung HDTV to replace the Panasonic, and there is no connection with either. Recently I bought the 10 foot cable assuming my cable was defective...this one doesn't work either. I've tried different ports, and with both cables my computer (in SL and W7) sees that there is a TV connected, but the TV only says "no connection" when I connect it to my MBP. Anything I should be doing to make this work?