[TheStorm]

This is from Quake3, migth be the same (just a little different error text)

ERROR: MAX_PATCH_PLANES

A visible brush face is being split too many times. Extra vertex points are created on visible face edges, where they are split by other visible face points (corners, or vertices). So if you have too many visible face points touching the edges of another face, that particular face will be split many times and have many vertex points.