My Sony VPL-CS4 is refusing to switch on most of the time (just the orange On/Standby light showing) and if I can get it to come on it won't switch off - if I press the on/off button the Menu display appears. I have to unplug at the mains to switch off. Does it need a reset of some sort (and if so does anyone know what sequence of buttons to press?) or is it something more serious? Thanks.