Same thing here, found this as I was pulling my hair out trying to figure out what's wrong with either my computer or how I was doing it. The lifting trick didn't work for me similarly have put a few days into a design (probably the most complex thing I've built so far) and now can't finish it. It just hangs on "Split faces 2" for me. Does anyone have a solution? Are there other good programs out there that would read the .mcx files??