Sorry for triple posting, but I have some more info that may or may not be
useful.
When enabling verbose output from glretrace, I can see that the next to last
operation before a hang is always glBindBuffer (I've run it 10 times) even
though the rest of the output is very different. This, however, only happens
when double buffer visuals is enabled, if I disable it using --sb the output is
the same as above, ending with glXSwapBuffers.
Not sure if this is a coincidence or not, but it seemed interesting to me.