I'm encountering the same problems with Build Mesh freezing at ca. 90% on the 'Calculating vertex colours...' step.
Configuration: PS v 1.2.3_2331; Build Mesh settings: height field, face count=low(10,000), source=sparse cloud. I've had the same error three times, including leaving the system for 20 hours with no progress (this should not be memory limitations, as this is a small job on a very high spec system that has previously handled much larger jobs). There is also no response when I attempt to terminate the process (the time elapsed counter simple continues for several more hours).