Very slow network directory listing - but fast data transfer speed once listed?

Question

Hello,
I have really tried to sort this myself before opening up to the community, however I have run out of ideas, and hope someone can offer the magic solution I have missed.
I am currently using the 3.4ghz i7 iMac on a 1GB LAN, running OSX10.7.2 - connecting to a Windows Server 2008 (Running Release 2) over ethernet.
If i go to a network directory that i haven't recently accessed it can take up to 60 seconds to show the contents of that directory. Once i have accessed that folder, if i come out of it and go back in it will be instant again - but the first time it lists the directory it looks like i have opened an empty folder - which after anything from 10seconds to 1 minute will suddenly show the files that are there.
Internet connectivity is fast through the network, and file transfers across the LAN are fast. (showing as approx 300mb per second) I can play and edit HD content across the network with no slowdown so I am confident that this issue is not related to the network speed itself, and is more to do with a setting on this mac.
Symptoms are very similar to this post: https://discussions.apple.com/message/12245148?messageID=12245148&amp%3b#1224514 8 - however i understand that in OSX Lion - SMB was removed - so i cannot find this file to edit.
I have tried bypassing additional hubs in the network by wiring direct cables to the switch that is connected to the file server, this made no difference.
I have also tried disconnecting the ethernet cable, and running over wifi. This fixes the listing problem, but when editing HD content over a network drive, this connection is not fast enough to carry the data without interruption (some projects are linked to up to 900gb of hd video content!)
Using ethernet, I have tried DHCP, DHCP with manual address, and manual mode. All reproduce this problem. i have tried using the windows workgroup, and tried without it.
I have also followed this suggestion: https://discussions.apple.com/thread/2134936?threadID=2134936&tstart=45 and used OpenDNS. this did not fix the issue.
For argument sake, I have also just tested a Macbook Pro running Snow Leopard to see if it was OS related. This reproduces the exact same problem, near instant directory listing on the wifi, a long and arduous wait on ethernet.
I cannot work out why directory listing is instant over wifi, but not over ethernet on 2 different macs, running 2 different versions of OSX. I also do not understand why if the network is having trouble listing the directories - the data transfer speed is 300mbps when i copy files across the wired network from the file server to the mac.
Does anyone have any other ideas as to what could be the problem here? We are about to start work on a very large project, where the content we are editing is spread out across around 200 different network folders (different shoots captured over the past 2 years). We really don't have the time to wait 60 seconds each time we need to access one of those directories to look for a file, and I am very close to pulling all my hair out!
I really look forward to hearing from anyone who can offer any insight.

Answer 1

If you are suspecting that the Windows update had something to do with your LAN going slow, then try the following:
1.  Look for updates for your clients LAN NIC driver; or
2.  Un-install the updates.