Hi Peter, thanks for sending me the 3DM file through e-mail, I've already sent you back a reply but basically it's not a Mac-specific issue, this particular file is unusually memory consumptive and kind of sluggish generating the mesh on Windows as well.

It seems that the file has excessively dense UV trim curves in it, my guess is that probably the original STEP file had a too small value for its file tolerance labeled in its header - currently the STEP importer uses whatever tolerance is specified in the file itself when it has to do some calculations on the data (particularly when creating UV curves from the 3D edge curve data), and if the tolerance labeled in the file has been set to some kind of unusually small value it can result in strange heavy UV geometry. Anyway, that's my guess on what is happening, we can sort it out further through e-mail.

Thanks,
- Michael