So generally about once per game I will freeze up for about 30 seconds -- which freezes not only me, but everyone else in the game.  Once things start moving again my graphics are totally broken (see pic).

Now, my first thought was that my video card was overheating (although I've never had a temp problem before playing other graphic intensive games i.e. Fallout3 / Oblivion).  However, if temp was the problem, I would not expect the following "fix" to work... As long as I'm playing in windowed mode, I can minimize then immediately maximize when this happens, and it fixes the graphics entirely, and I go on like nothing ever happened.

I have the most recent WHQL detonators (from 7/2).  Happened before that update, and has continued since.  Here are specs.  Thanks in advance for any ideas.

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System Information
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Time of this report: 7/5/2009, 15:01:41
   Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 2 (2600.xpsp_sp2_gdr.050301-1519)
           Language: English (Regional Setting: English)
System Manufacturer: System manufacturer
       System Model: System Product Name
               BIOS: Phoenix - AwardBIOS v6.00PG
          Processor: AMD Athlon(tm) 64 X2 Dual Core Processor 5400+,  MMX,  3DNow (2 CPUs), ~3.0GHz
             Memory: 2046MB RAM
          Page File: 354MB used, 3584MB available
        Windows Dir: C:\WINDOWS
    DirectX Version: DirectX 9.0c (4.09.0000.0904)
DX Setup Parameters: Not found
     DxDiag Version: 5.03.2600.2180 32bit Unicode

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Display Devices
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        Card name: NVIDIA GeForce 8800 GT
     Manufacturer: NVIDIA
        Chip type: GeForce 8800 GT
         DAC type: Integrated RAMDAC
   Display Memory: 512.0 MB
     Current Mode: 1440 x 900 (32 bit) (60Hz)