I need to go out for about an hour, but will check in to see the words of wisdom and the jokes when I return.
First line of defense, restart in safe mode, wait until the help screen about safe mode appears (if you can get into windows in safe mode), then restart normally and see if it works. Sometimes updates get a little wonky. How long have you had the laptop and how long do you run it per week?
This sounds eerily familiar to a HD error (bad sector write) during updates on a laptop I just repaired - eventually the HD just died and had to be replaced.
“There is an outside chance (although I did not see it) that my cat walked on the keyboard while the laptop was unattended.”
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Ridiculous. Cats don’t walk on keyboards at night...they play World of Warcraft online.