I just updated system-config-samba-1.2.99-1.fc18, I meet the problem when I press OK of "Create New Samba User".
In the terminal it prompts: "sh:/usr/bin/smbpasswd: No such file or directory"
I searched smbpasswd, and found there is a soft link at:
/usr/share/bash-completion/completions/smbpasswd, but this soft link links to smbclient in the same directory.
Confirmed it is fixed this morning.
*** Bug 889662 has been marked as a duplicate of this bug. ***