win98 can't find PDC while changing password

[Ma Gui Sheng]

	I am sorry if the question has been dicuss before, but I just can't find the 
answer from the maillist.
	I build a samba PDC on a redhat 6.0 , the samba version is 2.1prealpha (that
is the HEAD-branch?)
	I want to change the password on my clients, including NT Workstation,
NT plain Server, and win98. But these client all can't change password. Win98
told me "Couldnot find the PDC of this domain", NT Workstation & Server told me 
"The username  or your old password is not correct". While I could not find any 
piece log mesg on log.%m about Win98 situation, but find NT give the mesg of 

 [1999/08/03 21:57:26, 5] rpc_parse/parse_samr.c:make_samr_r_chgpasswd_user(5091)
  make_r_chgpasswd_user
[1999/08/03 21:57:26, 5] rpc_parse/parse_prs.c:prs_debug(36)
  000000 samr_io_r_chgpasswd_user
[1999/08/03 21:57:26, 5] rpc_parse/parse_prs.c:prs_uint32(160)
      0000 status: c000006a
[1999/08/03 21:57:26, 5] rpc_server/srv_samr.c:samr_reply_chgpasswd_user(1598)
  samr_chgpasswd_user: 1598
[1999/08/03 21:57:26, 10] rpc_server/srv_pipe.c:api_rpc_command(764)
  called api_samr_rpc
[1999/08/03 21:57:26, 5] rpc_server/srv_pipe.c:create_rpc_reply(90)
  create_rpc_reply: data_start: 0 data_end: 4 max_tsize: 5680
	
	I check the err code from the nterr.h and  find it is
"#define NT_STATUS_WRONG_PASSWORD (106)".
	How can I change password on the client I mentioned above?
	Can anyone mail his successful experiecne to me?