Since my latest System Update (I'm guessing the culprit is the BIOS Update to v 1.16-1.09, which was one of the updates that got installed), I've lost the ability to wake my X120E from sleep via the external keyboard and mouse. Normally this is enabled via the "allow this device to wake the computer" option for the device in question in Device Manager, but since the update that option no longer appears for either my external keyboard or mouse. Any ideas?
I also have BIOS update 1.16-1.00 installed in February, and I've had this same problem since then. "Allow this device to wake the computer" is now grayed out everywhere I'd like it to be on. It's somewhat annoying. I used to be able to use my laptop in desktop mode with an external screen, mouse & keyboard, and I could keep the lid closed, sleeping & waking with the keyboard Sleep button. Now I can put it to sleep, but not wake it. It was a nice feature to have, hope someone out there has a workaround.
I have downgraded my BIOS to 1.15-1.08 (the Lenovo downloads area has a repository of older BIOS's) and I can once again wake up my system from an external USB keyboard. The 1.16-1.09 BIOS appears to fix an issue with power management and Wake-on-LAN. If that fix is unimportant to you then installing the downrev BIOS may be the right choice. It seems to work for me.