Solution: If you get this error message, you have either misspelled your username or entered the wrong password. This could mean that you have forgotten your password, or that your account has been hacked. To be sure, you should contact a moderator in-game and ask him to check your account for suspicious activity. If it turns out your account was hacked, the hacker will be dealt with accordingly by the moderator, and your account will be locked to prevent further damage to it.
If you can not log into your account, you can go to http://support.dreamscape317.net/ and submit a recovery ticket. The support team will then investigate your accounts, and can change both your registered email and password. It can take up to 48 hours before a ticket is replied to.