I'm experiencing this too, however on amd64 (and no Nvidia modules - Intel GM45 chipset here). My un-scientific estimate of when this started to happen is approximately 2 weeks ago.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/844957 Title: Safely removing external (usb) hdd's can cause a kernel panic or system freeze To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-settings-daemon/+bug/844957/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
