[Samba] random errors "the local drive name is already in use. This connection has not been restored."

[yves.lejeune at kodak.com]

Hello,
 
I have random errors that I can not analyze nor fix:
when several users connect to the same Samba share, they get sometimes 
error messages
"the local drive name is already in use. This connection has not been 
restored", although the connection
is still usable afterwards. This sometimes breaks a file operation.
Clients are running Windows 2000, and the server is a Solaris 8 machine, 
it runs Samba 3.0.4.
After this I can often see that Samba still holds locks about files which 
are not used any more.
 
Is this a known symptom for Samba 3.0.4 ?
I have seen that many bugs are fixed in newer Samba versions, but I can 
not tell if they could be related to my problem.
 
In fact the problem might be related to code I wrote: my Samba is 
configured to load a specific VFS module,
which makes external database queries, among other things.
As a result the file operations are quite slow, and the result of some 
file operations may not be 100%
as Samba or Windows expect them to be....
 
Would you know a way to sort out the problem, e.g. something like a 
SMB protocol analyzer (for networking newbies...) ?
Or a way to know why Windows clients disconnect (if they decide to 
disconnect, rather than get disconnected) ?
Or would you know problems about slow Samba servers ?
 
Thanks in advance for your answers,
Yves Lejeune.
yves.lejeune at kodak.com