We have installed 300 Samba 3.0.6 Server as Fileserver as Workgroup Server , to 
share Word and Access files for Windows XP SP1 . In some cases the following 
error occures:

File Server stops responding for ca. 30-60 sek. At this time we have following 
logfile :

[2005/04/13 19:18:11, 0] smbd/oplock.c:oplock_break(841)
  oplock_break: receive_smb timed out after 30 seconds.
  oplock_break failed for file Vorlagen/Adreßköpfe/NORMAL.DOT (dev = 303, inode 
= 392881, file_id = 17013).
[2005/04/13 19:18:11, 0] smbd/oplock.c:oplock_break(913)
  oplock_break: client failure in oplock break in file 
Vorlagen/Adreßköpfe/NORMAL.DOT
[2005/04/13 19:18:11, 0] smbd/reply.c:reply_lockingX(4629)
  reply_lockingX: Error : oplock break from client for fnum = 13075 and no 
oplock granted on this file (Vorlagen/Adreßköpfe/NORMAL.DOT).

We can reproduce this erorr with a special set of own Word Templates, when we 
create a new Word file. After this error the network perfomance seams to be 
poor (Redirector turn off the oplock / cache ) until you reboot the windows 
machine. In your test-lab the updated samba 3.0.11 server have the same 
problem. In all this cases when the error occurs , I permit the network is fine 
and we can see the error if only one client is working. 

See also BUG 1801