Another thing to check is cooling. Bryce and other rendering programs will take your CPU up to close to 100% and the (cpu) temperature will rise accordingly. My notebook runs at around 37 degrees centigrade during normal operation but will go straight to 58-60 degrees when rendering a scene. A dirty heat sync or a cooling fan that's failing (or failed) will cause problems. It's easy to check and should be done anyway, every few months. Another question would be, can you repeat the crash? Does it crash at the same point each time with a specific scene?