NEC Plasmasync 42mp2 - Horizotal Screen Lines

[Granvil]

Hi Guys, I'm new to all this stuff so please bear with me if I ask really stupid questions.
            Couple of months ago bought the above mentioned Plasma (from that well known auction site) the only problem it had was sever screen burn (red) which having only paid £35.00, i could live with. About two months ago i moved into a new flat and was able to finally wall mount and set the whole thing up properly for the first time, no sooner had i done so and it developed a thin black horizontal line across the top of the screen (2" from the top). This would come and go for the next few days after which it was joined by an even thicker line about an inch below. These lines now seem to be permenant and now also total six !!  The original line plus two thicker lines below and other thin lines that seem to appear and disappear. This annoying problem happens no matter which input i use, and also masks out even the on screen menu.

Dumb question No. 1 - Anybody know what the problem might be ? and can it be repaired ?

Dumb question No. 2 - Could it be a cabling problem ? - i have a skybox connected with scart via an upscaler/tv tuner, from there to the plasma a dvi cable (plasma does not have scart input)

                  I'd really appreciate some advice on this problem - I've tried everything I can think of, and certainlly cant afford the expense of having it sent off for repair. Any help from you guys would be very welcome. MTIA