Can you provide more details regarding the "little white dots"? How extensive are the dots?
E.g., when and how do the dots occur or appear? HD SD, 3D?
What have you attempted to do to fix the problem - try another known working HDMI cable perhaps? Any troubleshooting via the User Guide/Manual?
Do the little white dots occur with all incoming video sources: DVD players, DVD recorders, direct connnectivity via ISP/cable service?
What model Mitsubushi do you have? Any warranty left?
Just need a few more details please.