i have this same problem and it happened when i upgraded my video card to a 6600gt. multiple clear lines moving up and down only really noticable on a blank desktop doesnt effect games much..
i had this problem before except it was colors and it was caused by a magnetic force nearby usually a subwoofer or a speaker, however this is not the case for me anymore. It doesnt really bother me but I do notice it and would like to know how to fix it.
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