I believe what farmerman was getting at had nothing to do with tipping the TV over - I think he was referring to what is called a "Hard Reset", accomplished through an extended period (several minutes at least, overnight is generally good) of the unit being disconnected from mains power - unplugged. Often, this will cause the unit to clear all previously user-defined settings, re-initialize and present its setup menu when next powered up and turned on.
From what you've said so far, it seems to me there is no other explanation than a display settings issue; something, overwhelmingly likely available through the set's menu, is affecting the display. I suggest again you locate and consult the set's user guide/owner's manual, which, if you don't have a hard copy, should be available through the set vendor's website support pages, and even if not, should be something you can order from the vendor.
When all else fails,
Read
The
Fine
Manual - always a good place to start