Actually this looks like a NVidia MCP5x bug, as explained there : http://marc.info/?l=linux-ide&m=136297331308023&w=2
** Bug watch added: Linux Kernel Bug Tracker #48951 http://bugzilla.kernel.org/show_bug.cgi?id=48951 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1181878 Title: Driver for hdd Western Digital Caviar Black 500 GB / 1 TB prevent suspend To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1181878/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs