In massing if you select a surface and create a divided surface. Now change the grid spacing to distance. Remove the distance displaying , type in 2 (i.e. 2mm) and do nothing for a few seconds.
You are very likely to get this Revit crash error:
I’ve reported the problem to Autodesk.
The work around is; if you are going to use distance for your grid spacing, select the grid and edit the spacing form the element properties dialogue box, rather than the options bar.