Thomson sky+box jammed?

Our sky+box was jammed on standby, we've done all the things previously mentioned, ie holding in the backup button to update & holding in the two other buttons whilst turning power on. Sometimes we can get the green light to come on & then get the sky channel but when you change channel it will show channel & whats currently on but we don't get no picture or sound. We took the hard drive out & tested it with my pc which says there dont seem to be a hard disc problem, has anyone got any other ideas before I buy a new one? One other point, it does seem a bit odd that alot of the problems mentioned seem to be happening to boxes just outside the warranty!