[VB, Framework] Certains windows marchent pas

Bonjour, je suis stagiaire en informatique au Canada (mais je suis francais), j'ai repris une application developpée en VB.net (sur Visual Basic 2003). Je n'ai apporté que quelques modifications mineures, et maintenant, l'application plante à l'affichage de la 3e fenetre sur certaines machines tournant sous XP et sous Vista.
En fait ca ne marche que sous XP, les machines sous lesquelles ca marchent possedent le Framework 1.1, le pack francais, le Framework 2.0 et un correctif (KB886903) Hotfix du Framework 1.1.

Sous les autres machines voici mon message d'erreur :

"An unhandled exception has occured in your application. If you click Continue, the application will ignore this error and attempt to continue. If you click Quit, the application will be shut down immediately.
Classe non enregistrée.
Details
See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.Runtime.InteropServices.COMException (0x80040154): Classe non enregistrée
at System.Windows.Forms.AxHost.CreateInstance()
at System.Windows.Forms.AxHost.GetOcxCreate()
at System.Windows.Forms.AxHost.TransitionUpTo(Int32 state)
at System.Windows.Forms.AxHost.CreateHandle()
at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
at System.Windows.Forms.AxHost.EndInit()
at Epandage.f_saisie_matos.InitializeComponent() in C:\Documents and Settings\A_POTTIEZ\Bureau\Logidose\f_saisie_matos.vb:line 415
at Epandage.f_saisie_matos..ctor() in C:\Documents and Settings\A_POTTIEZ\Bureau\Logidose\f_saisie_matos.vb:line 22
at Epandage.f_saisie_matos.get_DefInstance() in C:\Documents and Settings\A_POTTIEZ\Bureau\Logidose\f_saisie_matos.vb:line 428
at Epandage.f_donnes_princp.bt_valid_Click(Object eventSender, EventArgs eventArgs) in C:\Documents and Settings\A_POTTIEZ\Bureau\Logidose\s_donnes_principales.vb:line 1082
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.ControlNativeWindow.WndProc(Message& 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: file:///c:/windows/microsoft.net/framework/v1.1.4322/mscorlib.dll
----------------------------------------
System
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.573
CodeBase: file:///c:/windows/assembly/gac/system/1.0.5000.0__b77a5c561934e089/system.dll
----------------------------------------
System.Drawing
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.573
CodeBase: file:///c:/windows/assembly/gac/system.drawing/1.0.5000.0__b03f5f7f11d50a3a/system.drawing.dll
----------------------------------------
Logidose
Assembly Version: 1.0.2711.14715
Win32 Version: 1.0.2711.14715
CodeBase: file:///C:/Program%20Files/Logidose/Logidose.exe
----------------------------------------
System.Windows.Forms
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.573
CodeBase: file:///c:/windows/assembly/gac/system.windows.forms/1.0.5000.0__b77a5c561934e089/system.windows.forms.dll
----------------------------------------
System.Xml
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.573
CodeBase: file:///c:/windows/assembly/gac/system.xml/1.0.5000.0__b77a5c561934e089/system.xml.dll
----------------------------------------
Microsoft.VisualBasic
Assembly Version: 7.0.5000.0
Win32 Version: 7.10.3052.4
CodeBase: file:///c:/windows/assembly/gac/microsoft.visualbasic/7.0.5000.0__b03f5f7f11d50a3a/microsoft.visualbasic.dll
----------------------------------------
Accessibility
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.573
CodeBase: file:///c:/windows/assembly/gac/accessibility/1.0.5000.0__b03f5f7f11d50a3a/accessibility.dll
----------------------------------------
AxInterop.MSFlexGridLib
Assembly Version: 1.0.0.0
Win32 Version: 1.0.0.0
CodeBase: file:///C:/Program%20Files/Logidose/AxInterop.MSFlexGridLib.DLL
----------------------------------------

************** 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."

C'est la premiere fois que j'utilise VB, et je n'ai pas eu de formation sur ce langage (je ne connaissais que Java, C, C++), donc j'ai appris par internet, mais je ne comprend vraiment pas pourquoi ca ne marche pas sous certaines marchines et pas d'autres.