I think Morph targets also kill P5 firefly. It could be memory or simply calculating the geom to send off to the renderer. I have also found certain combos of displacement and smoothsahding flags cause locks. For example, turn on smooth shading in the render options then set displacement on an object and turn off smooth shading for that object. Seems to cause hiccups for me. It could also be they used STL when they coded P5 or in firefly. The stock STL in MSVC has a habit of doubling mem usage when a vector, set, map etc reach their allocated sizes. So even if an object needs say 64 megs, when stl hits the limit it wants to realloc 128 megs. That's just a wild guess and it could be countless numbers of things wrong. Its just odd since I have had these locks across different machines. For example I can render a scnee fine in firefly on one of my machines but can't on another machine.