shazmart

Hi all, after much patience by one of your kind experts, i`ve learned to programme my own tit card...brilliant! BUT, sometimes, after a short while, the picture freezes then goes blank and then shows the message;"not running or scrambled". If i change channels then go back...it`s back on! This may be an obvious or simple thing that is part of the package, so appologies if i`m being picky. Is there something i`m not doing correctly or does this happen to everyone else?