Every now and then I get disconnected from the server for no apparent reason.  My ping is generally low (60s) and my gaming PC is not particularly stressed.  Today I was getting disconnected several times in a row, so I decided to check some logs.  I launched CoD, and selected a server.  Then I pressed (shift ~) to watch the scrolling log.  I was getting multitudes of errors like this:

PERFORMANCE WARNING: occlusion thread is tracing when client wants to update for 5 frames...
PERFORMANCE WARNING: occlusion thread is tracing when client wants to update for 7 frames...
PERFORMANCE WARNING: occlusion thread is tracing when client wants to update for 6 frames...
PERFORMANCE WARNING: occlusion thread is tracing when client wants to update for 5 frames...
PERFORMANCE WARNING: occlusion thread is tracing when client wants to update for 10 frames...
PERFORMANCE WARNING: occlusion thread is tracing when client wants to update for 12 frames...
PERFORMANCE WARNING: occlusion thread is tracing when client wants to update for 10 frames...
PERFORMANCE WARNING: occlusion thread is tracing when client wants to update for 5 frames...
PERFORMANCE WARNING: occlusion thread is tracing when client wants to update for 6 frames...
PERFORMANCE WARNING: occlusion thread is tracing when client wants to update for 5 frames...
PERFORMANCE WARNING: occlusion thread is tracing when client wants to update for 8 frames...

Google had little help, but I did see that people were hinting that graphics drivers might be an issue.  Since I always keep my drivers up to date (Nvidia 9800GTX) I checked to ensure they were the latest.  Yup, same drivers since May.

I then decided to check my Nvidia control panel and went into the "manage 3D settings" menu.  I selected CoD WaW for the game, and checked my gfx card settings.  for whatever reason, the default behavior for my "Mixed GPU Acceleration" was set to multidisplay.  Additionally, my Vsync was set to "on" and my Threaded Optimization was "on".  I changed GPU acceleration to single display, set everything else to auto, or to "controlled by application."

I launched CoD again, and checked the logs, and I have zero errors like the ones pasted above.  Moreover, I haven't been kicked since.  
I have no clue if I actually solved anything, or if it was purely a coincidence but it's working for now, and I'm not complaining.

Give it a try.

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im giving it a go, will let u know, thanks!

Not sure if this is the problem the the first thing that came to mind was the occlusion error maybe part of the new addition to Nvidia drivers.  It is called ambient occlusion and is supposed to enhance the 3d environment with a hit to FPS.  You can access it in the Nvidia control panel  Can't say weather this has something to do with the problem but since you set everything to auto and you are fine it maybe off by default or not being accessed.  Have seen threads where people are using it with W@W.  I haven't really messed with it yet but now I gotta try it.

Perhaps you're referring to the new PhysX functionality in the last round of drivers?  I made sure I looked throughout the control panel for "occlusion," though I did note that PhysX was new and enabled/on.  
I did not change my PhysX settings from the default setting (on).

As a side - I've experienced server disconnects in the previous drivers as well..just not as often as today.

Another notable thing was, I made sure my CoD WaW graphics an texture settings matched my Nvidia settings.  For example, Anisotropic filtering is Auto (or application controlled) in both places.

I'll keep researching, as I did see other server/client errors, though it doesn't seem to affect game play.

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Here is a definition of Occlusion Culling, as defined by Nvidia.  After reading this, I do vaguely recall a setting in the Nvidia control panel that had something to do with rendering (maybe maximum pre-rendered frames???).  I'm on my laptop now (read: no nvidia card here) and will check my settings for such ASAP.

29.1 What Is Occlusion Culling?

Most graphics algorithms show us how to render something quickly, or how to make it look nice. Some techniques favor performance, while others aim for quality, but the challenge is how to strike a balance between the two.

Occlusion culling increases rendering performance simply by not rendering geometry that is outside the view frustum or hidden by objects closer to the camera. Two common types of occlusion culling are occlusion query and early-z rejection.

This chapter examines the occlusion query and how to use it properly, including two examples proving how efficient occlusion culling can be. Because one of the examples relies heavily on the usage of bounding boxes, these will also be covered, just to make things more understandable.
29.1.1 Occlusion Query

Starting with the GeForce3 GPU, all NVIDIA GPUs (and many from other vendors) have included the occlusion query feature, which lets us avoid rendering occluded objects. By skipping the entire rendering process for an occluded object, we can reduce the rendering load on the GPU.

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Ok.  I'm bumping this up, as I found my errors were coming back up and i was getting kicked form the servers.  I learned that there are other contributing factors.  Some of this might be obvious to you, but to others its a little easy to overlook.  ALSO NOTE: Windows update will often offer up downgraded/older driver releases.  Be sure you know what versions you have first.

1.  Make sure you have the latest version of DirectX 9.c  I thought I had the latest version, but it turns out my DX9 was from November 08.  I am now patched up to 3/2009.
go here to get the latest version!  http://www.microsoft.com/downloads/details.aspx?FamilyId=2DA43D38-DB71-4C1B-BC6A-9B6652CD92A3&displaylang=en

Download it, run the installer, and then reboot.  

2.  Make sure your audio drivers are current.  I have Realtek HD integrated audio and learned that my codecs were from 2006.  Make sure you find the newst versions!  I went to my motherboard website to get drivers, but they weren't as new as the one directly from Realtek.  Install your audio drivers and reboot.

3.  Graphics drivers.  Everyone knows this one...I checked today, and sure enough there was a 6/18/2009 update for Nvidia gfx cards.

The Occlusion Errors have subsided for now.  My guess is that the DX9 update resolved that problem, since occlusion (as we've learned) is a graphics/rendering term.

Edit:  I did check my punkbuster versions as well.  they are the latest and "greatest"

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Tripod you bring up a very good point.  In our hast to troubleshoot a problem weather it be cars, appliances and the computer sometimes the obvious is over looked.  We all know Nvidia spits out new drivers all the time but Microsoft and Evenbalance is reaally overlooked (at least with the message board folks) that there is an update.  They think the end user will stay up to date on there own.  To make sure you have the best experience with applications is to make sure you have all the latest updates for the given application.  And we all know that with online gaming this could be more than one.