I have been experiencing screen lockups and fatal errors during online play for a couple of months now. I ran DxDiag and nothing seems to be out of order, I'll paste it below.
MOST of the time, it will occur when I am talking on vox or someone else is transmitting, but not always. It does not seem to make a difference if my screen is filled with eye candy or not - the last two times I was in the middle of a large body of water with no land in sight.
I will be flying along and suddenly everything freezes (last sounds continue to repeat) for about 20 or more seconds, then I will warp back (if I am in buffs, drones sometimes are shooting out ahead of me, etc.) and then I hold my breath to see if it will do it again. Usually I get a second, fatal screen freeze that mirrors the first, but this time at the end of the freeze the sounds stop, but the screen is still frozen. Sometimes my Windows mouse pointer will come into view when I move it, sometimes not. I had to learn the keystrokes for rebooting from the "Aces High has encountered an error and will not run" message. I always send an error report to MS, then reboot. Re-launching AH results in instant error message.
My netstatus and pings are usually very good. I always shutdown everything else before playing, so no AV, etc. is running, just the basics of XP after running EndItAll and Task Manager to shut down the garbage.
It is to the point that I get one or more dumps EVERY time I fly now. It is usually the reason I end up logging off. 
Here is my DxDiag report:
------------------
System Information
------------------
Time of this report: 10/13/2006, 12:38:33
       Machine name: HOME
   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: Dell Computer Corporation
       System Model: Dimension 8100               
               BIOS: Phoenix ROM BIOS PLUS Version 1.10 XP2
          Processor: Intel(R) Pentium(R) 4 CPU 1800MHz
             Memory: 512MB RAM
          Page File: 340MB used, 909MB 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
------------
DxDiag Notes
------------
  DirectX Files Tab: No problems found.
      Display Tab 1: No problems found. DirectDraw test results: All tests were successful. Direct3D 7 test results: All tests were successful. Direct3D 8 test results: All tests were successful. Direct3D 9 test results: All tests were successful.
        Sound Tab 1: The file tbcwdm.sys is not digitally signed, which means that it has not been tested by Microsoft's Windows Hardware Quality Labs (WHQL).  You may be able to get a WHQL logo'd driver from the hardware manufacturer. DirectSound test results: All tests were successful.
          Music Tab: No problems found.
          Input Tab: No problems found.
        Network Tab: The registry information for the DirectPlay application 'FlightSimulator' is missing or damaged.  You should reinstall that application.
--------------------
DirectX Debug Levels
--------------------
Direct3D:    0/4 (n/a)
DirectDraw:  0/4 (retail)
DirectInput: 0/5 (n/a)
DirectMusic: 0/5 (n/a)
DirectPlay:  0/9 (retail)
DirectSound: 0/5 (retail)
DirectShow:  0/6 (retail)
---------------
Display Devices
---------------
        Card name: NVIDIA GeForce4 Ti 4600
     Manufacturer: NVIDIA
        Chip type: GeForce4 Ti 4600
         DAC type: Integrated RAMDAC
       Device Key: Enum\PCI\VEN_10DE&DEV_0250&SUBSYS_00000000&REV_A2
   Display Memory: 128.0 MB
     Current Mode: 1280 x 1024 (32 bit) (60Hz)
          Monitor: Plug and Play Monitor
  Monitor Max Res: 1600,1200
      Driver Name: nv4_disp.dll
   Driver Version: 6.14.0010.7189 (English)
      DDI Version: 9 (or higher)
Driver Attributes: Final Retail
 Driver Date/Size: 4/1/2005 16:16:00, 3980288 bytes
      WHQL Logo'd: Yes
  WHQL Date Stamp: n/a
              VDD: n/a
         Mini VDD: nv4_mini.sys
    Mini VDD Date: 4/1/2005 16:16:00, 3454656 bytes
Device Identifier: {D7B71E3E-4110-11CF-A57F-0A2003C2CB35}
        Vendor ID: 0x10DE
        Device ID: 0x0250
        SubSys ID: 0x00000000
      Revision ID: 0x00A2
      Revision ID: 0x00A2
      Video Accel: ModeMPEG2_A ModeMPEG2_B ModeMPEG2_C ModeMPEG2_D 
 Deinterlace Caps: {212DC722-3235-44A4-BD29-E1652BBCC71C}: Format(In/Out)=(YUY2,0x3231564e) Frames(Prev/Fwd/Back)=(0,0,2) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_PixelAdaptive 
                   {212DC723-3235-44A4-BD29-E1652BBCC71C}: Format(In/Out)=(YUY2,0x3231564e) Frames(Prev/Fwd/Back)=(0,0,1) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_MedianFilteri ng 
                   {335AA36E-7884-43A4-9C91-7F87FAF3E37E}: Format(In/Out)=(YUY2,0x3231564e) Frames(Prev/Fwd/Back)=(0,0,0) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_BOBVerticalSt retch 
                   {212DC722-3235-44A4-BD29-E1652BBCC71C}: Format(In/Out)=(NV12,0x3231564e) Frames(Prev/Fwd/Back)=(0,0,2) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_PixelAdaptive 
                   {212DC723-3235-44A4-BD29-E1652BBCC71C}: Format(In/Out)=(NV12,0x3231564e) Frames(Prev/Fwd/Back)=(0,0,1) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_MedianFilteri ng 
                   {335AA36E-7884-43A4-9C91-7F87FAF3E37E}: Format(In/Out)=(NV12,0x3231564e) Frames(Prev/Fwd/Back)=(0,0,0) Caps=VideoProcess_YUV2RGB VideoProcess_StretchX VideoProcess_StretchY DeinterlaceTech_BOBVerticalSt retch 
         Registry: OK
     DDraw Status: Enabled
       D3D Status: Enabled
       AGP Status: Enabled
DDraw Test Result: All tests were successful.
 D3D7 Test Result: All tests were successful.
 D3D8 Test Result: All tests were successful.
 D3D9 Test Result: All tests were successful.
-------------
Sound Devices
-------------
            Description: Santa Cruz(tm)
 Default Sound Playback: Yes
 Default Voice Playback: Yes
            Hardware ID: TURTLE_BEACH\SANTA_CRUZ_WDM_INTERFACE
        Manufacturer ID: 1
             Product ID: 100
                   Type: WDM
            Driver Name: tbcwdm.sys
         Driver Version: 5.12.0001.4193 (English)
      Driver Attributes: Final Retail
            WHQL Logo'd: No
          Date and Size: 6/23/2003 12:15:14, 554304 bytes
            Other Files: 
        Driver Provider: Voyetra Turtle Beach
         HW Accel Level: Full
              Cap Flags: 0xF5F
    Min/Max Sample Rate: 8000, 48000
Static/Strm HW Mix Bufs: 96, 95
 Static/Strm HW 3D Bufs: 96, 95
              HW Memory: 0
       Voice Management: Yes
 EAX(tm) 2.0 Listen/Src: Yes, Yes
   I3DL2(tm) Listen/Src: Yes, Yes
Sensaura(tm) ZoomFX(tm): Yes
               Registry: OK
      Sound Test Result: All tests were successful.