If you try to use certain characters as your user or network name K++ won't let you such as *. To get around this edit your user and network name in the windows regestry.
User Name: HKEY_CURRENT_USER\Software\Kazaa\UserDetails\USERNAME
Network Name: HKEY_CURRENT_USER\Software\K++\NETWORKNAME
One Limitation I've Found is you can't use @ as your network name.
I haven't tried it yet, but maybe you could also use this to get past the user and network name length limitation.
My username is @@@@@@@@@****