Dancing pixels?

[jugglingom]

I'm experiencing a sort of staticky look in my render. The pixels seem to kind of dance in the image. It's most noticeable in the horizontal lines of a bump-mapped brick, and also in the reflective floor of the scene. I originally thought it might be an interlace problem, but it showed up before being dumped to video.
After searching 21 pages of posts here, I decided to ask if anyone has encountered the same and might know how to fix it. I've played with the alias settings, but it doesn't seem to make a difference.

Thanks
Rob Gray