Ok maybe have a look in the service menu. Two things to try:
– Look for a ‘BtB’ setting and see if you can turn it off. (This is the Business to Business software that the TV would have used when it was in a Hotel).
– If the above doesn’t work, you could try the TV’s ‘reset to default’ that should be in the ‘Monitor’ part of the service menu.
Also it may be worth trying another hdmi -> DVI lead – they are not all wired the same way.