I've managed to reproduce the slowdown here with UpdateNormals and the Dwarf model (could have sworn it didn't happen before). I'll have a look at it.
Simon, we owe you big time for sharing MiniB3D. I will follow your example by releasing our cross BlitzMax /C++ game framework as open source as soon as we have v 0.1 ready. It was developed so I can prototype games in BlitzMax and then port them in no time to C++.