I have a mac book OS X 10.5.8. I had been using my hd tv as a monitor. Now the screen doesn't display on the tv. When I go to system preferences and select display it doesn't give me the arrangement option and says there is only one display connected to my computer even when my adapter is plugged into the port. I don't know if it is the adapter or the port that is not working is there a way to diagnose this?