Sony with brightness problem...
 

I have a Sony KV-X2993E 100Hz whit a problem. When a dark object
appears in a bright picture, the picture turnes darker besides the
dark object. The same thing happens whit a bright object on dark
picture. The picture turnes brighter besides the object. When you're
watching the set these symtoms shows upp like bright horizontal
flashes on the screen. What can cause this?

also when there is i bright picture, and i activate the on-screen menu
that is pretty dark, the rest of the picture goes brighter...