It's happened twice now, both times while holding a configurator with the mouse pointer and moving it around on the screen. Not sure of the exact trigger, but it appears to be the same exception both times, and I've only seen it happen with that GUI open (although I just spawned in this configurator while trying to debug the infuser, and haven't extensively tested other scenarios).

I'm not sure if people still need the gigantic FML logs or not, so I'm including them too.

First:
https://dl.dropboxusercontent.com/u/203721/crash-2014-07-20_21.47.30-client.txt
https://dl.dropboxusercontent.com/u/203721/fml-client-3.log

Second:
https://dl.dropboxusercontent.com/u/203721/crash-2014-07-20_22.16.44-client.txt
https://dl.dropboxusercontent.com/u/203721/fml-client-latest.log

Fixed, thank you!