Can't help you on what the fault is but I had (and at times continue to have) the exact same problem. As have many other people (you'll see this if you do a google search). This has been happening to my tv for about 2 years or so on and off. It happened again about 4 weeks ago for about 5-6 days. I know this sounds crazy but when it happens I turn off the tv, give it a few bangs on the back and it works when I turn it back on. Again, I know it sounds crazy but it has worked for me on repeated occasions!