Switching to the "nv" driver, and uninstalling nvidia-glx-185 makes glxinfo and Xorg not crash any more, so it seems this problem is localized to the non-free drivers.
Switching to the "nv" driver, and uninstalling nvidia-glx-185 makes glxinfo and Xorg not crash any more, so it seems this problem is localized to the non-free drivers.