Vista - Explorer disconnected shares

Hello,
I'm facing a strange issue when using explorer to create a file or a folder
on a network share, it takes about 100 secs to complete. Checking on the
server itself the file/folder is created instantaneously but the client is
waiting, waiting before displaying it. A complete folder structure copy to
the same share is working at a decent speed.
If I use another "explorer" like freecommander, the files/folder creation
is immediate. In addition to that it is not happenning all the time and not
on all the shares on the same server (example : Share A is bad 90% of the
time on 90% of the clients and Share B is bad 20% of the times on all PCs,....).

The behaviour is the same in SP1, I tried also to disable Offline files and
indexing, I forced also the folder template "Documents" and to "Notspecified".
The "netsh interface tcp set global autotuning=disabled" and "netsh int tcp
set global rss=disabled" are done as well

I ran a Wireshark and a Processmonitor and found that the ProcessExplorer
displays a "DISCONNECTED" just after receiving the reply of the file creation,
and waits a long time before trying to reconnect. I'm looking in two directions
:

1. Reduce the timeout between the DISCONNECTED and the re-connection, but
I don't know what I should modify.

2. Fix this strange issue.


Any help would be welcome

Patrick