username login error

We have a new person register and was unable to log-in to our blog. I was unable to log in using their username and password as well. I logged-in as administrator and deleted the user and re-registered them. Still unable to log-in due to a username error. I deleted the user and re-registered them removing the space in the username, did not help. I deleted the user and re-registered them changing the username to only the first word. Every thing worked just fine.

Can someone please tell me why Nelay Cotoer or NelayCotoer will not work as a username but Nelay will? I have searched and am unable to find an answer. Is their a syntax or format that the username must conform to?

If there are some specific requirements for the username it would be nice to present the information at the register screen for new users. (administrators)

I did used Firefox for me and Explorer for the new user. To make sure I did not have any cookie problems and I refreshed the screen several times.

Thank you
Ken
http://foodblog.jkvetter.com