My Quarry is Drunk (moving diagonally?!?)

[iamtotus]

I built a 64x64 Quarry with 9x9 dimensional anchors on two of the corners (just to be extra paranoid). It assembles without issue and appears to start mining...but it's mining in a diagonal pattern and it seems to just be doing the same path over and over again.

Here is a gif I assembled from a few screenshots, couldn't find anyone else who had this problem.

http://makeagif.com/media/2-09-2013/MhF9zb.gif

I've tried powering the quarry down, I've tried removing it, redoing the land marks, then doing it over again, all with no success. I've made a few 16x16 quarries in the same area without a problem as well.

Any ideas on why this is happening / how to fix it? I'm at a loss.