To prevent someone else from stealing your password, password forms for e-mail sometimes lock if you attempt to enter your account with the wrong password too many times in a set period. If you find that a password form is locked, there are a number of ways that you can unlock it. The easiest thing to do is to wait for it to clear.
Use the "Contact Us" link on the bottom of your e-mail login page. Call or e-mail (from another account) the customer service number for the email program. Explain that your account has been locked and why. They might be able to unlock it for you, if you can prove you own the account.
Clear the cache of your computer, as sometimes the password lock appears as a saved or cached page, when in reality you are not locked out of your account. Clearing the cache is done in different places depending on the browser you use, but you can find the option under "Options," "Tools" or the main menu for your browser.
You might want to try another computer or another location, as sometimes the password lock feature is activated by IP address, and you might be able to access the form from a different IP.