This is because you have entered an extra character into you email which is not allowed for example ^ or a % sign. Make sure that the @ is the correct one and not something else. Sometimes copying your email addresses and pasting it in can fix the issue.
Also putting a space before or after your email will create this error. So make sure that you have only put your email address in without spaces.
Also please make sure you are clicking the log in link and not the sign up link. You cannot log in through the sign up form.