I tried setting the movecode to 0 earlier, and it always seems to crash me with a message along these lines:
Unknown HVAR (61,5) (set 0)
ProcessLevel - process.vc (62)
--where the line is in ProcessLevel of process.vc, of course. The 61 is constant in every version of this error, so I presume it refers to entity.movecode, and the number after it ("5" here) seems to be the entity index.