Ello, I have a mac pro and I run it through my 50" LG tv via a dvi to hdmi cable it has worked fine for approx 3 years no issues, recently I turned it on and I would get "no signal" on the tv, I changed the hdmi input and it still didn't work however my sky box does work fine in either. For about 2 days it came back on again last week but now it's gone back to no signal again, I also changed the dvi input and no joy, is this likely to be the cable?

Could possibly be, have you changed the resolution by accident?