Hi Matthew,
I'm sorry to hear about your problem. It is really frustrating and makes the rendering impossible. I'd really appreciate if you could send a simplified reproduction of the problem through GS TechSupport after your deadlines. Our simple models seem to work - there may be some problem with complexity...
Regards,
Zsolt
Zsolt Táskai
ArchiCAD Development - GDL Team
AC13, AC14 and upwards...