Problem:

One of the users couldn't login to the site. After a few attempts the Sorry, there have been more than 5 failed login attempts for this account. It is temporarily blocked. Try again later or request a new password. message was displayed.
I entered the interface as admin, and went to this user's editing form. The user status presented was Active. I resetted the password, and tried to login as that user, but got the same error message.
So I used the request a new password link. I received the Replacement login information for <user> mail. I entered the link supplied in the mail and replaced the password, but this didn't solve it either.

The solution:

Enter the data base, and clean flood table. this releases the lock.
The query I used is:

It empties the entire table, but it is not a problem. Of course you can delete only the relevant records.