I've had a problem with this set for a few months now and I need some advise before I start messing around with it. There is a small 'patch' in the middle of the screen that appears as a bluish purple blotch when the background scene is muted, say the grey of a race track when watching F1. Black and white material shows the fault off even better, against a pure white background the blotch is a slightly yellow colour. It may be dust particles on one or other of the lcd panels, or the lens assembly, but I'm not too sure. If it was a CRT TV I'd say the screen needs degaussing but obviously not in this case. Any ideas?