horizontal lines in yafray render w DOF

maybe i just cranked it too high, but I was using DOF set fairly high, and the render came out full of horizontal lines. it looked like the matrix effect or something. anyone know what might be causing this? should I set more AA passes maybe? ( currently set to 2 ) should I put up the render? make a bug report? anyone else getting this behavior?

Two passes is probably not sufficient, especially if the aperture is relatively large (more blur), try 4 or more passes with 8-25 samples per pass. If possible, can you show an example?
There could be some problems in certain cases with GI.

I set it for more passes and turned the blur factor down to a reasonable level, and that seems to have taken care of it.