User account gets locked when trying to access mapped drive

We recently changed our security policies at work and set user passwords to expire every 60 days in GPO. Now time for people to change their passwords. A couple of users thus far have had no problems but, one user had problems. Having changed their password and then tried to access a mapped drive they get,

'The referenced account is currently locked out and may not be logged on to'.

Even if I removed the mapped drive, unlocked the account and then tried to map the drive again, the account would get locked.

I Googled and tried some suggestions with no result. What worked for me was, map the drive again and then click, 'Connect using a different user name' and type in users credentials, including the domain name.

i.e. '<domainname\username>' (mycompany\joebloggs) and their password.

This worked! Huh!???