It's expecting a password. Maybe it only supports harder encryption, in that case I (although you could do it yourself if you have the experience) would have to compile a version including that support. I'm not going to have spare time for that until after christmas, I'm afraid.
Maybe specifying a passwort is enough? Then just add "-password YOURPASSWORD" to the command line, like this:
Code:
./kvncviewer.sh -password YOURPASSWORD 192.168.2.1:0