Sit down to start work this morning at 8:30, load up PC and can't sign in to Windows, my keyboard doesn't work. Hmmm I think. Well, I'd been cleaning up yesterday, maybe I unplugged the cable whilst hoovering up behind the PC. Checked the cables, all seems fine there. Hmmm.
Software problem perhaps? I sign into Windows using the on-screen-keyboard. Check device manager and it tells me keyboard is working fine. Hmmm.
Try uninstalling and reinstalling keyboard, reboot windows, no improvement.
30 minutes later after all sorts of fiddling, it clicks! This keyboard takes batteries!
A change of batteries and I'm up and running. Lesson learnt: check batteries first.
Hey, it's Monday morning!