Hi Stephanie,
I've not heard of this bug, but I've had some difficulty with arbitrary_grids in the past. You might try using a covering_grid instead of an arbitrary_grid object since it is designed with grid-based datasets in mind whereas arbitrary_grids are more suited to particle-based datasets. This will give you a uniform grid at whatever resolution you desire (200 pc). If that doesn't work, perhaps it is a problem with your user-defined fields? But given that it works with cut_regions, I think it's unlikely to be your field definition.
Hope this helps!
Cameron