samba - May 2005 - Perf difference between Windows mapped drive and UNC share accessing Samba share?

we're using Samba 3.0.10 on a Mac OS X server (XServe), and are accessing
files on the XServe from Windows Server 2003.
 
for the specific situation of creating thumbnails of images, i'm seeing a
huge perf difference between accessing the same file via mapped drive vs.
UNC path.
 
if we map the Z: drive to \\usseast01\assetstorage (Z:\foo.tif), and create
a thumbnail of a 1.5MB TIFF file, it takes 2-3 sec.
 
if i access the same file via UNC path (\\usseast01\assetstorage\foo.tif),
i'm seeing times anywhere from 30 secs, to upwards of 2 min, to create a
thumbnail of the exact same file.
 
are there any known reasons when going over Samba for this kind of perf
difference?  could there be an obvious configuration problem in Samba or
Windows which could cause this (i.e. authentication?).  
 
my guess is that using a mapped drive pre-authenticates the connection,
while going via UNC share does not.
 
thanks for the help,
Kirk
 
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Kirk Marple
Chief Software Architect, VP of Engineering
Agnostic Media, Inc.
e: kirk@agnostic-media.com
w: www.agnostic-media.com <http://www.agnostic-media.com/> 
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