Flashing pixals on MATSUI 42P900

[mainstreem]

Hi there, I am having problems with my MATSUI 42P900 plasma screen.

I have been getting these flashing pixels all over the screen now for the last few months.
it's most noticeable in the dark/black areas of the picture....looks like snow. ( like on old tv's when not tuned in right)

I have tweaked with the V up and V down pots on the back and got a great picture. however, coming back to turn it on again this morning and its back to the way it was.

I have located a repair kit for around £90 for all 3 boards on-line. but can anyone help me with any tips or can anyone suggest something that i may not have thought of yet before I go out and spend $$$

is this due to over heating?
could it be something else than the Ysus board?
I have sound and like I said, when I adjusted it with V settings, it seem to get a lot better but keeps returning to the state it was in before.

Anyone else had this problem?

any help would be really appreciated

Thanks guys.

cheers