Strange purple lines in windows - Benq FP241W, 8800GTX

  I get thin horizontal shiny purple lines on the screen, different levels vertically, that appear and disappears quickly. They appear a short time after windows start up. First I wondered if it was artifacts but running 3D Mark 06 actually helps, I see them more seldom or it might just be me, having a harder time noticing them. They don't increase in number anyway. Most often is just one or two at the same time. When I shut down windows, right before the computer shuts down - then there are around seven, eight at the same time, definately the time where I "see them best".

My components are:
Benq FP241W 24" computer screen with drivers from Benq (digital)
8800GTX with latest nvidia drivers
E6400
Corsair 6400 2GB
2 WD320GB harddrives
Gigabyte GA-965P-DS3

They weren't visible when I first installed windows, at least not that I noticed.
Anyone that can help?