[Samba] Only option "force user = root" give file locking

[czechj]

I have two Windows XP clients accessing the same shared file, user1 has
the file open. User2 then opens the
same file, receiving no warnings about the file being open by another
user. File is modified by user1 and saved and remains open. File then
modified by user2 and saved. File closed and opened by user1 who
sees only modifications made by user2.

user1 (WinXP) open test2.ods

smbstatus:
Locked files:
Pid          Uid        DenyMode   Access      R/W        Oplock SharePath
Name   Time
--------------------------------------------------------------------------------------------------
14758        10004      DENY_WRITE 0x2019f     RDWR   EXCLUSIVE+BATCH
/work/samba/bazafirm   test2.ods   Wed Aug  1 17:50:15
14758        10004      DENY_NONE  0x100001    RDONLY     NONE
/work/samba/bazafirm   .   Wed Aug  1 17:49:47

user2 (WinXP) open file:
smbstatus:
Locked files:
Pid          Uid        DenyMode   Access      R/W        Oplock SharePath
Name   Time
--------------------------------------------------------------------------------------------------
14787        10002      DENY_WRITE 0x2019f     RDWR   EXCLUSIVE+BATCH
/work/samba/bazafirm   test2.ods   Wed Aug  1 17:55:38
14787        10002      DENY_NONE  0x100001    RDONLY     NONE
/work/samba/bazafirm   .   Wed Aug  1 17:55:12


But when I use option "force user = root" tha file lock works OK!!!

user1 open file test3.ods

Samba version 3.0.25a
Locked files:
Pid          Uid        DenyMode   Access      R/W        Oplock 
SharePath
Name   Time
--------------------------------------------------------------------------------------------------
2103         0          DENY_WRITE 0x2019f     RDWR      EXCLUSIVE+BATCH
/work/samba/bazafirm   test3.ods   Thu Aug 16 05:32:28


user2 open file test3.ods (file is open "read mode")

smbstatus:
Locked files:
Pid          Uid        DenyMode   Access      R/W        Oplock 
SharePath
Name   Time
--------------------------------------------------------------------------------------------------
2103         0          DENY_WRITE 0x2019f     RDWR       LEVEL_II
/work/samba/bazafirm   test3.ods   Thu Aug 16 05:32:28


Why? This is working only if I set option "force user = root"???