i found this:
(put that site in your favorites!)
A. This usually happens with large maps, it occurs when you have 256+ vertices on one face, which reminds me of the MAX_POINTS_ON_WINDING which has a limit of 64 vertices touching one brush, so its odd how it can even happen. Anywho you need to rectify the error by not having so many vertices on one brush!
so i think you made a brush with way to much vertices