Long lag with Windows network I am the sole Mac user in a Windows shop (graphic designer / video editor) and as such mount a Windows share to store all my working files on. I'm experiencing horrific lags from time to time (not always, and not immediately replicatable), particularly when I'm using anything from CS5 (although it's happened when loading MS Word files or moving items through the finder, too). I get the beach ball of doom for up to two minutes (on rare occasions I have to force the application to quit) when I'm loading / saving / placing files (anything where it has to go out to the network share).

I'm reasonably certain that the connection to the windows mount is what's causing the problem as when I move the files to a local firewire drive and work from that I don't have any of these issues. I have 1G+ right to the desktop, and it's not a consistent thing(sometimes I can work all day from the network share and sometimes I have to literally force applications to quit and work locally).Web connections generally aren't affected (I had a separate issue that was fixed by turning IPv6 connections off.

Local IT guy is a Windows fanboy so he's not a lot of help; since it's my personal machine I've sort of taken the view that it's my problem, but I am wondering if anyone here might have any thoughts. I'm connecting using smb; I believe everything (DHCP, firewalls, etc.) is being overseen by a Server2008 box.
From here

(specifically noted to help with Snow Leopard / SMB / Windows Server 2008)

Launch the Terminal (Applications/Utilities/Terminal).

You can use the vi or the pico editors included with Mac OS X to edit the smb.conf file by typing sudo vi /etc/smb.conf or sudo pico /etc/smb.conf. [Note, as always when changing system files, back up the original first]

You will be prompted for a password, utilize the password for your admin account.

I used vi. In order to change anything within the file you will need to put vi into insert mode by typing the letter i (at the bottom you will see the word insert). 

Some handy vi editor tips: vi has 2 modes: 'Command Mode' and 'Insert Mode.' To switch between modes you use the letter i in Command Mode to switch to Insert Mode and when in Insert Mode you use the Escape key to switch to Command Mode. File saves are done in Command Mode and edits to the file are done in Insert Mode. You can search the file you are editing in Command Mode by typing /searchstring where searchtring is what you are looking for in the file.

Scroll down to the line use spnego = yes and change the yes to a no.

Continue to scroll down to stream support = yes and change this to no, on the line immediately below that says ea support = yes change this to no.

In the next group that says darwin_streams:brlm = yes change this to no.

Save the file by first taking vi out of insert mode by pressing the Escape key. Then to save the file and quit vi type :wq and press Return.

Restart your Mac.