Can't change password from Windows

[Andrew Golubev]

Hello :)

Samba 2.2 as PDC
smb.conf
.....
unix password sync =yes
encrypt passwords = yes
passwd program = /usr/bin/passwd %u
passwd chat = "New UNIX password:" %n\n "Retype new UNIX password:" %n\n
"passwd: all authentication tokens updated successfully" 
....
Ofcourse passwd chat string look like passwd dialog.  
When I try to change mu password from nt dos session by "net user username
newpassword /domain" I got an error - "System error 5"\n "Access failed" 

What wrong?

Thank You for help,
Andrew