I just spent the last 7 minutes entering and re-entering passwords because the error on sign-up stated "Enter a valid value" The 2nd password field content was removed leading me to believe that my passwords didn't match. I tried a simple one, a longer one that was more secure, retried these 2x, moved to yet another version and finally opted to login using Google. (which I didn't want to do)
It was only at this point that the error message came back and informed me that valid user names can only contain letters, numbers and underscores. My first.last name was not valid.
2 problems here:
* Error messaging needs to be more informative (field and value)
* Need better qualifiers on user name and pword parameters for that matter.