I assume it's the CK that crashes and not the game (given the thread title)... depending on what it is you're trying to do, it WILL crash predictably. An instance I found of this is when you try to load a custom NIF in the renderWindow... when that NIF has the wrong format/data. That was back when CK was first released (and preCK using the GECK, but they aren't THAT different)... I don't recall exactly what caused the CK to crash, but here's some NIF-related instances that I know will crash the game itself (usually at the Title/Main Screen or when that NIF is told to render).
- any custom-made, concave collision (eg: using the old 3DSMax plugin, exporting a 'packed strips')
- multiple nodes sharing the SAME bsLightingShaderProperty node; there must be copies of the node made and each mesh inside the NIF pointing to a different one
- activators with anim_static motion combined with the setVehicle() setup (which is additional bsFadeNodes and custom collision arranged a certain way)
What is it that you're trying to do that makes it crash?