The website has several security rules. If you try to log in wrongly more than 3 times, your user will be temporarily blocked (1 hour). After that time you can try to log in again, if the problem persists contact us so we can help you. Sometimes this will be reflected with a popup window that will have a jquery or jvascript error message.
Remember that if you forget your password you can create a new one by following the procedure explained in the login form, where you will receive an email link to reset your password.