Mac mini display problem...

I have a mac mini thats a couple of years old (thinks its a 1,6ghz cpu intel). The computer is used as a mediacenter, and is connected to my samsung lcd tv trough DVI-HDMI cabel. In recent time i have gotten som flickering and screen stripes when im using the mac mini. The flickerings isnt always there, just sometimes. The first time i think it got fixed by me just reconecting the cable to the mac mini. The next time i got the problem that did not work, so i tried to put the computer to sleep, and wake it again. This worked. What can be wronge? Whats most likely, hardware or software error?