@bilalakhtar: soulsource just added his similar experience with AMD, so I don't think this is specific to NVidia.
I discovered that there is a tool which is supposed to test for Unity 3D support. I don't know if this is used to decide whether to fire up Unity 3D when you log in, but on my system it incorrectly reports that Unity 3D *is* supported, so that may explain why my system hangs when I try to log in with the default session. Here is the output of unity_support_test: OpenGL vendor string: NVIDIA Corporation OpenGL renderer string: GeForce 8800 GTX/PCI/SSE2 OpenGL version string: 3.3.0 NVIDIA 280.13 Not software rendered: yes Not blacklisted: yes GLX fbconfig: yes GLX texture from pixmap: yes GL npot or rect textures: yes GL vertex program: yes GL fragment program: yes GL vertex buffer object: yes GL framebuffer object: yes GL version is 1.4+: yes Unity 3D supported: yes -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/894132 Title: unity does not start using xinerama and multi-monitor To manage notifications about this bug go to: https://bugs.launchpad.net/unity/+bug/894132/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs