I'm running RHEL 6 on one of the machines that I regularly use. I recently updated to firefox 37.0.1 from firefox 36.0.4 and now it crashes when I try to play Conclave.
I've had problems with it crashing on other websites as well, but only Conclave crashes every time I open it.
I have never had any problems under firefox 36.0. or earlier versions. It seems OK on firefox 37.0 on Fedora 21 as well.