I suspect something's up with the bbPress support. I've tested Crayon on two different test sites, one with the latest bbPress 2 installed, the other without.
On the site with no bbPress, Crayon installs successfully. On the site with bbPress installed, Crayon fails. Upon activation, I get a white screen. The Plugins admin menu becomes unavailable in the same way.
The plugin did seem to have been activated though, and I was able to successfully test it. Other than this hickup on the backend, it appears to be working brilliantly!