Substances causing Unity 4.5.3 and 4.6 to crash on play?

I’ve tried opening a project in the latest version of Unity 4.5.3 and also the 4.6 beta and when i hit play, Unity would crash. in the crash log it said:

Anyway, I narrowed it down to my substances that are in the assets folder. I deleted these and it’s working fine.

Anyone else having issues with this?

Me too. This made me crazy…

Just tried to repro it in a new project & I can’t