ThinkPad Question:
Discussion
you could try disconnecting the cmos battery to fully reset the bios back to factory settings.. ..outside of that, maybe clean the keyboard motherboard connections with DeoxIT.. ..but then again, it might be some screwy microsoft driver issue
I may have found the solution. There's a chipset update in Lenovo System Update. Since applying that update, the problem with the keyboard not working seems to have gone away.
I'll keep testing.