While I was out, someone attempted to guess my phone password. They couldn't guess it and now it displays the 'too many password attempts' screen, which needs to be unlocked with a google account. However, my google account is not working. I enter the username and password correctly, and have attempted to do so about 10 times. So why is it not unlocking? Do I need an internet connection to unlock it?
You won't need an internet connection.
Also, when typing the username/email, make sure you have either @gmail.com or @googlemail.com at the end, depending on what it was when you added the account.
If you didn't add anything, the default for android <= 2.3 is @googlemail.com