What you are experiencing is a failure of DMD(Digital Micromirror Device) actually.

I have seen this problem on Mitsubishi and many other brands of DLP TVs, as well. Most of the time the entire light engine is either replaced or worked on. Each spot (pixel) that you view in the picture is made by a single mirror moving back and forth on the DMD. In total, there are over a million of these tiny mirrors, and the white spots you see are those mirrors that have stuck in the "On" position. These mirrors get jammed and hence this problem.

I recommend contacting Mitsubishi Consumer Relations at(NNN) NNN-NNNN to ask (emphatically insist) that they cover the cost of the repair. They may very well supply the optical engine(part no.938P126040) at no charge or small charge, with you paying the labor; but, it doesn't hurt to keep trying for the labor cost, too. Sometimes they will offer you a rebate on new set. If your set is under extended warranty then you won't have to spend a penny. Else I would guesstimate this repair would cost you around $1200. I have seen major companies like Sony, Samsung, Mitsubishi considering it as premature failure of light engine if the TV is less than 4-5 years old.

They will have to come and check the set onsite first before they can offer a concession. Hence you will have to call them and place a request.

Please do not rate unless you are not satisfied. If you feel like rating "Bad Service/I expected more" or "Poor Service/Helped a little", please stop yourself from rating and continue the conversation. I want you to be a happy and satisfied customer.

If you feel I have helped, please click on any of the smiley faces after the second one from left to accept and rate my answer.

Regards,

Pramit