Comment 37 for bug 1734147

@tobia; contact Lenovo support. If USB does not show up, it's not an Ubuntu issue. Your USB system may be failing, or the USB key is not recognized (which would make it not show up as a boot option). You might want to try with a different USB key. Was 'ubuntu' listed before under UEFI? You should also not change the boot settings unless you know what you are doing, as doing so can obviously keep your system from booting correctly. If things are being reset at boot (presumably after a few seconds of delay at a blank screen), then you might be dealing with a bad firmware; you should contact Lenovo for help to upgrade or revert the last firmware update.

@Alexis Rico (sferadev); I suspect your hard drive is failing, or you are dealing with a bad firmware. GRUB would not cause this. What options are you trying to change in BIOS? What happens exactly when you try it? Is there an error, does it allow you to save, but then you get a blank screen for a while, and the system "reboots" again?

@bruno; as above: what happens? What settings do you try to change? What happens exactly when you do? What precise steps do you take?

In general, if you are unable to save setting changes in BIOS, you *need* to contact Lenovo support, especially if at "reboot" you see a blank screen for a while before anything happens. This may mean the firmware is confused, and its safety mechanisms will attempt to recover by settings back to their defaults.