HDMI output Mac mini PLEASE HELP

Hi all. I have a Panasonic HD TV that I would like to use as my output for my Mac Mini audio. The thing is, it has always been my output and it has always worked. RANDOMLY, yesterday it stopped working and it switched to my internal speakers. Now, everytime I try to switch back to Panasonic output ( I click on it ) The sound still comes out of the internal speaker. Please someone help this is very annoying and i dont know why this is happening.