Hi,
First of all, you should know I stopped editing the files manually and I'm currently using only your editor 
 
Then, I met another problem. I added many pictures into Bmp_TechIcons.bmp as I have many new techs. To do so I increased the height of the bitmap and added 5 lines of pics. However, while the image reference of 169 is ok in the game, the editor complains about it:
CG_Claws:
 * Invalid Picture # 169: e:\jeux\space empires v\Pictures\UI\Bmp_TechIcons.bmp only contains images [1 - 168]
EDIT: one more consequence is the impossibility to see the tech tree while the problem remains:
See the end of this message for details on invoking 
just-in-time (JIT) debugging instead of this dialog box.
************** Exception Text **************
System.ArgumentNullException: Value cannot be null.
Parameter name: image
   at System.Drawing.Graphics.DrawImage(Image image, Int32 x, Int32 y)
   at System.Drawing.Graphics.DrawImageUnscaled(Image image, Rectangle rect)
   at Se5Editor.TechAreasForm.panelTechTree_Paint(Object sender, PaintEventArgs e)
   at System.Windows.Forms.Control.OnPaint(PaintEventArg  s e)
   at System.Windows.Forms.Control.PaintWithErrorHandlin  g(PaintEventArgs e, Int16 layer, Boolean disposeEventArgs)
   at System.Windows.Forms.Control.WmPaint(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Mes  sage& m)
   at System.Windows.Forms.ControlNativeWindow.OnMessage  (Message& m)
   at System.Windows.Forms.ControlNativeWindow.WndProc(M  essage& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
************** Loaded Assemblies **************
mscorlib
    Assembly Version: 1.0.5000.0
    Win32 Version: 1.1.4322.573
    CodeBase: <a href="file:///d:/windows/microsoft.net/framework/v1.1.4322/mscorlib.dll" target="_blank">file:///d:/windows/microsoft.net/framework/v1.1.4322/mscorlib.dll</a>
----------------------------------------
Se5Editor
    Assembly Version: 1.3.0.0
    Win32 Version: 1.3.0.0
    CodeBase: <a href="file:///D:/Documents%20and%20Settings/thuylvain.MAIN/Mes%20documents/SEV/Space%20Empires%20V%20Editor/Se5Editor.exe" target="_blank">file:///D:/Documents%20and%20Settings/thuylvain.MAIN/Mes%20documents/SEV/Space%20Empires%20V%20Editor/Se5Editor.exe</a>
----------------------------------------
System.Windows.Forms
    Assembly Version: 1.0.5000.0
    Win32 Version: 1.1.4322.573
    CodeBase: <a href="file:///d:/windows/assembly/gac/system.windows.forms/1.0.5000.0__b77a5c561934e089/system.windows.forms.dll" target="_blank">file:///d:/windows/assembly/gac/system.windows.forms/1.0.5000.0__b77a5c561934e089/system.windows.forms.dll</a>
----------------------------------------
System
    Assembly Version: 1.0.5000.0
    Win32 Version: 1.1.4322.573
    CodeBase: <a href="file:///d:/windows/assembly/gac/system/1.0.5000.0__b77a5c561934e089/system.dll" target="_blank">file:///d:/windows/assembly/gac/system/1.0.5000.0__b77a5c561934e089/system.dll</a>
----------------------------------------
System.Drawing
    Assembly Version: 1.0.5000.0
    Win32 Version: 1.1.4322.573
    CodeBase: <a href="file:///d:/windows/assembly/gac/system.drawing/1.0.5000.0__b03f5f7f11d50a3a/system.drawing.dll" target="_blank">file:///d:/windows/assembly/gac/system.drawing/1.0.5000.0__b03f5f7f11d50a3a/system.drawing.dll</a>
----------------------------------------
************** JIT Debugging **************
To enable just in time (JIT) debugging, the config file for this
application or machine (machine.config) must have the
jitDebugging value set in the system.windows.forms section.
The application must also be compiled with debugging
enabled.
For example:
<configuration>
    <system.windows.forms jitDebugging="true" />
</configuration>
When JIT debugging is enabled, any unhandled exception
will be sent to the JIT debugger registered on the machine
rather than being handled by this dialog.
(I hope I am clearer than last time...)