Particle Systems break editor...where do i start debugging?

I'm getting the weirdest error for a while now and I haven't been able to track it down, does anyone have an idea?

In my main VR project which is enabled for both Oculus and SteamVR runtimes, if I click on a particle system, or add a fresh default particle system to the scene, the editor goes absolutely nuts. It displays the first few sprites of the particle system in pink, then starts filling the screen with grey triangles. The editor UI starts crapping out and becomes unusable. It is still semi-responsive and I just have to save, close, and re-open Unity to fix it. Here is a screenshot.

see how scene window is filled with grey junk, and editor UI chrome and sybols are all messed up?

I've tried deleting all unused plugins and hunting around for an offending script but I can't figure out what is doing it. It does it on multiple computers, and it doesn't do it if i start a fresh project, so it definitely seems like something particularly broken in this codebase.

Thanks for your debugging ideas!
Ian

 

Also I should add, this was happening in 5.6 and now still in 2017.1

 

A further note, the particle effects fire just fine in play mode. And i can even click on them in the inspector in play mode and nothing goes wrong. It is only when I click on them in Edit mode that the crazy screen effects kick in.