I've found myself in a bit of a confused state. I upgraded a machine from Ubuntu 12.04 LTS to 14.04 LTS, and have now lost USB keyboard input. (And possibly lost other USB input devices, but I can't tell as it boots to textmode console only) Keyboards work in BIOS and at the Grub prompt, but not after the kernel has booted. The machine was previously running the 14.04 kernel, so that hasn't actually changed. If I boot the machine with a USB key running a fresh version of Ubuntu 14.04, the keyboard works fine too. I've tried several keyboards, and every combination of USB-related option in the BIOS to no avail. I assume that somewhere in the past couple of years, I've modified something on this machine which is now conflicting with something that's been upgraded.. but I have no idea what. I can get at the filesystem to edit things via the bootable USB version of Ubuntu. Any ideas of what to try? Cheers, Toby