I have a new iMac which I'm attempting to connect to my Sony KDL-46S5100 LCD Television via HDMI. The TV will not recognize the computer. I have confirmed that my adapter and cable work by testing the connections on a MacBook Pro - that worked fine. However, when I plug the adapter into my iMac the TV says "no signal" and the iMac does not recognize the TV. I went to the Apple store earlier and they were able to get the computer to connect to their TV with no problem. ANY suggestions?