I am using wordpress multisite and buddypress the usernames are restricted to use only lowercase when a uppercase is used in the username then I get the error message,
Usernames can only contain lowercase letters (a-z) and numbers.
Like to know is there any working plugin or code change I could do to allow usernames to have capital letters.
You can do that by adding this to your functions.php :
More info in the codex : http://codex.wordpress.org/Plugin_API/Filter_Reference/sanitize_user