mitsubishi 55513 wavy screen problem

I have a mitsubishi reare projection 55513.  It has worked well for a couple years, now the entire screen is wavy.  I changed inputs, and no matter the picture source, it is wavy.  the waves are horizontal in appearance.  The only thing i have noticed is that sometimes my family will turn off cable box at night so tv is black, and not turn off tv power.  Any help is greatly appreciated.