Bug#407055: Compiz breaks the X server if the other head doesn't have DRI
I have a similar setup and a similar need, but differently from the
described scenario, compiz breaks my X server when I try to start it.
I think the difference from my case to the other case reported here is
that I don't have any support for DRI in the other head, instead of
having a bad DRI.
I'm attaching the log from the server just before the break, I think
this can help. As this bug not only makes compiz unusable, but also
affects another programs, I'll raise it's severity.