   Weird Runtime Error with C# application
  When ever my brother runs this app, and I click on a combo box, i get this JIT error dialog. Anyone know why?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: item   at System.Windows.Forms.ComboBox.ObjectCollection.AddInternal(Object item)   at System.Windows.Forms.ComboBox.ObjectCollection.Add(Object item)   at Krygier_Web_Surfer.Form1.cbHistory_Click(Object sender, EventArgs e)   at System.Windows.Forms.ToolStripItem.RaiseEvent(Object key, EventArgs e)   at System.Windows.Forms.ToolStripItem.OnClick(EventArgs e)   at System.Windows.Forms.ToolStripControlHost.HandleClick(Object sender, EventArgs e)   at System.Windows.Forms.Control.OnClick(EventArgs e)   at System.Windows.Forms.ComboBox.WndProc(Message& m)   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)************** Loaded Assemblies **************mscorlib    Assembly Version: 2.0.0.0    Win32 Version: 2.0.50727.42 (RTM.050727-4200)    CodeBase: file:///C:/WINDOWS/Microsoft.NET/Framework/v2.0.50727/mscorlib.dll----------------------------------------Xiemsoft Web Portal    Assembly Version: 1.0.0.0    Win32 Version: 1.0.0.0    CodeBase: file:///C:/Program%20Files/xiemsoft/Xiemsoft%20Web%20Portal/Xiemsoft%20Web%20Portal.exe----------------------------------------System.Windows.Forms    Assembly Version: 2.0.0.0    Win32 Version: 2.0.50727.42 (RTM.050727-4200)    CodeBase: file:///C:/WINDOWS/assembly/GAC_MSIL/System.Windows.Forms/2.0.0.0__b77a5c561934e089/System.Windows.Forms.dll----------------------------------------System    Assembly Version: 2.0.0.0    Win32 Version: 2.0.50727.42 (RTM.050727-4200)    CodeBase: file:///C:/WINDOWS/assembly/GAC_MSIL/System/2.0.0.0__b77a5c561934e089/System.dll----------------------------------------System.Drawing    Assembly Version: 2.0.0.0    Win32 Version: 2.0.50727.42 (RTM.050727-4200)    CodeBase: file:///C:/WINDOWS/assembly/GAC_MSIL/System.Drawing/2.0.0.0__b03f5f7f11d50a3a/System.Drawing.dll----------------------------------------************** JIT Debugging **************To enable just-in-time (JIT) debugging, the .config file for thisapplication or computer (machine.config) must have thejitDebugging value set in the system.windows.forms section.The application must also be compiled with debuggingenabled.For example:<configuration>    <system.windows.forms jitDebugging="true" /></configuration>When JIT debugging is enabled, any unhandled exceptionwill be sent to the JIT debugger registered on the computerrather than be handled by this dialog box.
  umm...  looks like you're trying to add something to a combo box and it's null.  Check the stuff you've added to it and make sure none are null.   ;  As nickwinters said.By that exception it's probably something you've done in Krygier_Web_Surfer.Form1.cbHistory_Click(Object sender, EventArgs e)   