samba - Mar 2000 - Problems with "locking" files with SAMBA 2.05a on Linux

I have a SAMBA configuration on my Linux system which works fine except
for one detail :

If two users try to open the same file, the second user does not receive
the customary warning that the file is already open.

I've set the following on the share in an attempt to get the DENY modes
working, even though some of them seem to only be for byte locking.

 share modes = Yes
 locking = Yes
 oplocks = No
 strict locking = Yes

When the first user opens the file, a temporary file is created which
contains the name of the user opening the file, and has the same
filename except for the first two characters which are changed to
"~$".

When the second user opens the file, no warnings are given that the file
is already open.

HOWEVER

When the second user tries to save the file, he/she receives the
following error in windows.

There has been a network or file permission error. The network
connection may be lost.

Any pointers would be appreciated.

Cheers
Gordon