LOST MY GUIDE SCREEN?

I'VE LOST MY GUIDE SCREEN, I CANNOT ACCESS IT FROM EITHER THE GUIDE BUTTON OR THE MENU PAGE, IF I PRESS THE BUTTON THE SCREEN GOES BLUE, FREEZES AND THEN 2-3 MINS LATER THE BOX TURNS ITSELF OFF, 30 SECONDS LATER IT SWITCHES BACK ON AS IF NOTHING HAPPENED BUT STILL NO GUIDE SCREEN, THIS IS A PAIN AS WE CANNOT RECORD ANYTHING AND HAVE TO CHANGE CHANNELS VIA THE UP / DOWN BUTTONS. ANY IDEAS ?