LOGIK 19 INCH TV KEEPS SWITCHING SOURCE! How can I stop this?

Hi THERE, MY lOGIK 19 INCH FLATSCREE TV WITH DVD/FREEVIEW KEEPS SWITCHING ITS SOURCE FROM COMPONENT TO DVD WHILST SON IS PLAYING THE X BOX.IT DOES THIS RANDOMLEY SOMETIMES EVERY 30 SECONDS, THIS IS INCREASINGLY GETTING FRUSTRATING AS IT INTERUPTS PLAY AND HE HAS TO SWITCH THE SOURCE BACK WITH THE REMOTE CONTROL! ( IE YOU PICK SOURCE ON THE REMOTE, MOVE DOWN THE CATEGORIES ON THE SCREEN AND A TICK IS PUT NEXT COMPONENT INSTEAD OF DVD) HOW CAN I STOP THE TELEVISION FROM DOING THIS!