The other day MySQL Workbench somehow set the password for the localhost root account from None to some other value while I tried to change the password of another user. Don't know exactly what happened, but to rest the password you should:
- start mysql
- type "use mysql"
- type "update user set password='' where user='root';"
- type "flush privileges"
After this, the root account has no password. Note that without step 4 changes to the user table will have no effect whatsoever. Took me 30 minutes to find out ...