I do not allow spaces in the configuration backend but I do not see any setting to disable or enable to ALLOW hyphens - periods . in usernames. These usernames already existed prior to V4. Removing any users with these two characters from the usernames is not an option. How do I fix?
Have a look at this recent thread asking same question. http://www.amember.com/forum/threads/special-characters-in-username.16419/#post-63641 In particular post #2 might help. (I haven't looked through this particular script.)