Does anybody get a strobing effect when filming video with the D90? I often shoot indoors for interviews with my D90, but I often get a sort of strobing with it.  Check out the attached picture, to help you see it on a picture, I added red marking, so simply look on the curtain on the right of that.



My best explanation so far was the type of lighting in the room, which is common in most offices, similar that was is in the picture:



Does anybody know what is going on?
Similar experience?
Solution?
Explanation?

Thanks for any input.
You seem to be on the right tracks, fluorescent tubes are notorious for flickering and CMOS sensor is read row-by-row in video mode. 

Try shooting under window light and/or use your own lighting, e.g. a LED video light. Try shooting so there's not much office visible in background, you won't be able to light it all.