USB Keyboard and Mouse not working after applying Win 8.1 updates and Avast upgr

[REDACTED]

I am just going to throw this out there - has anyone experienced the USB ports not working after doing December updates and or Avast upgrade?  My neighbor had this happen on a Windows 8.1 Lenovo H505s desktop.  Keyboard works in BIOS fine.  Light comes on on keyboard until it starts to boot into Windows, then it goes off.  Of course you can't get by the lock screen (by touching any key) so that you can log in.  There are no PS/2 ports on the machine, so can't use an old keyboard.  I want to get in to uninstall the updates and/or remove Avast to figure out what caused the problem.  Of course can't boot into Safe Mode(not that it will matter cuz I think the keyboard still won't work).  Any suggestions?

Thanks 

[Asyn]

See: "If you cannot  Boot the computer"
Instructions: http://forum.avast.com/index.php?topic=53253.0

[REDACTED]

Thanks, but I can't do much without a mouse and keyboard.  It's a 64-bit Win 8.1 system.  I will try to boot with the 8.1 install DVD and try to repair.  I don't think this is virus related.  It started happening AFETR Win 8.1 updates and the latest Avast update were installed. 

[REDACTED]

And the answer was........boot with Windows 8.1 setup disk (had to allow legacy hardware in BIOS), and ran system restore from 12/10/15 - which was before the Windows updates.  Took a little while.  When complete, started up fine and keyboard and mouse worked.  Installed 11 Windows updates and still fine.  Upgraded Avast and still fine.  Must have been a corrupt file(USB driver?), because several reboots and still fine.  Created another Restore point for today after everything updated and working well.