I think I might have another bug report on my hands. Look at the attached screenie. I also attached the zgeproj file that causes this. When you open up the project and click on the ParticleModel object, the app gives me the error you see in the screenshot. It seems like the access violation happens when it's trying to render something in the Preview Window upon clicking the object.
Also I can't just click OK and continue working; I have to kill the ZGameEditor.exe process from the Task Manager.
Let me know if you need more info.
EDIT: Now I'm pretty sure it happens during whatever it's trying to do when trying to render the ParticleModel in the preview windows because I locked the Preview Window to another object and then clicked on the ParticleModel and no access violation occurs.
EDIT2: Ok, looks like I found the culprit. Adding a RemoveModel at the end of your OnRender state is NOT a good idea

-Yılmaz