Sorry for wasting your time, Cornflake.
Turns out it was neither a WP problem nor a computer problem. It was an all_white problem.
all_white wrote:
It says the password is incorrect, but I know it's not.
That statement was wrong.
I've just realised I was typing one digit wrongly. My password algorithm is so complex and has so many rules to it that I often get mixed up.
Anyway, I'm back now! Ready to play tug of war with you again!
Silly me! LOL