I have a similar problem...
My SONY KE-P42M1 plasma has developed a fault that usually occurs several hours after switch-on. It usually manifests itself as flickering multi-coloured horizontal lines mixed with some static although sometimes this is accompanied by a pulsing strobe effect. It's almost like some kind of interference but it happens on all inputs from different sources.
Dunguard, How long have you had this for, zazwpx
Usually answered in minutes!