I'm attempting to use the GLU nurbs functions to display trimmed nurbs, but have run into some problems. The first few surfaces I draw display just fine, but eventually, a GL_STACK_OVERFLOW exception is raised when gluEndSurface is called. It doesn't seem to depend on the surface itself. I get the error whether I display a short list of surfaces many times (e.g. rotating, etc) or a long list once. Eventually the stack overflow occurs. I think the problem is associated with trimming, because if I draw the surfaces without trimming, the error does not occur. I'm running Ubuntu Linux 9.04 (Mesa 7.6 libGLU), Nvidia drivers/core OpenGL, and pyopengl 3.0.0. I've duplicated the problem on an RHEL 5.4 installation.