Samsung LN46A530 LCD strange problem

[Fred75]

Samsung LCD TV Model LN46A530P1F

Problem: TV works fine when first turned on, after about 15 minutes the picture quality of the right 1/3 to 1/2 of the screen begins to degrade, first flickering, then three narrow (3mm) horizontal black lines flicker on the screen.  After that the right hand side goes dim and images begin to "smear".  After the TV is switched off for a bit the picture returns to normal.

Any suggestions on where to start?

Thanks