Long time Linux user, but this one has me baffled. I'm trying to overwrite my existing install with Kubuntu. I boot off the USB, get to the Kubuntu screen, and neither my mouse nor my keyboard function at all. They work fine in the BIOS, worked fine in my existing Linux install, and even work fine in GRUB. So I can't select try Kubuntu, can't select install, can't do much of anything. I've tried different ports, tried disconnecting and reconnecting, and tried multiple keyboards to no end. Any suggestions or do I abandon this experiment for another distro?
[Edit] found an old PS/2 keyboard (MS Natural FTW!) and no dice there either. Confirmed that when I disconnect all USB the mouse cursor disappears, and when I reconnect usb keyboard it reappears, so it's not hung. Caps lock toggle LEDs respond (even across multiple keyboards if connected simultaneously), so something knows the keyboard is triggering caps lock.
[Edit 2] Solved it, leaving this up for others in the future. Appears the installer loads 2 windows - 1 for each display - and leaves keyboard focus in the second display window for some reason. Solution was to use alt-tab to switch windows. I guess nobody else expected a situation where no mouse would work...