[Samba] Problems with oplocks (samba 3.0.24, Kernel 2.6.17)

[samba news]

Hi list!

We migrated from FreeBSD 5.2 with Samba 3.0.22 to samba 3.0.24 on Linux, 
Kernel 2.6.17. Some users are running foxpro programms on XP and W2K and have 
problems now concerning locked files. The old FreeBSD server never had such 
poornesses. I couldn´t find a solution searching the web but I tried out this 
smb.conf options:

kernel oplocks = yes
fake oplocks = No
locking = Yes
oplocks = Yes
veto oplock files = /*.DBF/*.dbf/*.MDX/*.mdx/*.NDX/*.ndx/
level2 oplocks = Yes
oplock contention limit = 2
posix locking = Yes
strict locking = Yes
share modes = Yes

Nothing helped. 

The questions now are:

Is it possible to run samba on Linux with clients using dbf without this 
hassles?
If so: How can I accomplish that?

Or is the only/easier way to go back to FreeBSD?

Hints and help would be much appreciated!
Regards,

Oliver