https://bugs.freedesktop.org/show_bug.cgi?id=80419
--- Comment #126 from Nicolai Hähnle nhaehnle@gmail.com --- That's interesting, because r600 is a different user space OpenGL driver. It might be an interaction with the DDX or kernel though.
If you cannot ssh from a different computer, you can still recover the log from e.g. /var/log/kern.log (the exact location may depend on the distribution).