The particle system uses some relatively advanced OpenGL features that are not used in other parts of the Clonk code, so I'd not be overly surprised if old drivers have problems with it. All OpenGL calls are made from the main thread as far as I can see. The particle thread might modify some data after pointers have been passed to OpenGL, however that parts are protected by locks, so I think OpenGL finishes access to that memory before it is modified. Also, the crash seems to happen when the OpenGL objects for particle rendering are created, not when actually drawing or accessing vertex memory. It probably happens as soon as the Clonk starts moving and making these puff particles.