I looked through the posts and didn't see this anywhere, so I hope I'm am safe from being flamed for not R.T.F.M.
I have v6.3.5 installed and it is working beautifully (for the most part); however, I attempted to register myself as a test user so I could play around, and received the following error message ("Sorry, the e-mail address entered has already been used to register a member." I know that this is false as I'm the only one on the board and I used a different e-mail address (Admin-related). So, I go back and enter a different e-mail address and receive this error message: "Sorry the Username you requested is already taken. Please choose another Username."
Oddly enough, I go back in under Admin and there are the people I signed up as with the e-mail address that I gave. 
Does anyone have any idea why this might be happening? Thanks in advance.
http://www.forepath.net/clusterfscked/mboard