10.6.8. Can't connect to server via cmd+k or Finder menu or command line. How to connected?
This question has some suggestions for enabling the missing menu option (that question is about 10.7, but worth a try).

I think the command line version isn't working because you need to provide a final argument, specifying where to mount the shared directory locally.  On my 10.6.8 machine, man mount_smbfs gives this example:

mount -t smbfs //username:userpass@myserver/PUBLIC /smb/public