An unhandled exception has occurred in the form's code
System.Security.SecurityException
Request for the permission of type 'Microsoft.SharePoint.Security.SharePointPermission, Microsoft.SharePoint.Security, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c' failed.
at System.Security.CodeAccessSecurityEngine.ThrowSecurityException(Assembly asm, PermissionSet granted, PermissionSet refused, RuntimeMethodHandle rmh, SecurityAction action, Object demand, IPermission permThatFailed)
at System.Security.CodeAccessSecurityEngine.ThrowSecurityException(Object assemblyOrString, PermissionSet granted, PermissionSet refused, RuntimeMethodHandle rmh, SecurityAction action, Object demand, IPermission permThatFailed)
at System.Security.CodeAccessSecurityEngine.CheckSetHelper(PermissionSet grants, PermissionSet refused, PermissionSet demands, RuntimeMethodHandle rmh, Object assemblyOrString, SecurityAction action, Boolean throwException)
at System.Security.CodeAccessSecurityEngine.CheckSetHelper(CompressedStack cs, PermissionSet grants, PermissionSet refused, PermissionSet demands, RuntimeMethodHandle rmh, Assembly asm, SecurityAction action)
at FormUserCodeLoadData.FormCode.FormEvents_Loading(Object sender, LoadingEventArgs e)
at Microsoft.Office.InfoPath.Internal.FormEventsHost.OnLoad(DocReturnEvent pEvent)
at Microsoft.Office.Interop.InfoPath.SemiTrust._XDocumentEventSink2_SinkHelper.OnLoad(DocReturnEvent pEvent)
则极大可能的原因是你没有设置信任级别，你需要在InfoPath表单里设置：
在 Tools 菜单, 点击 Form Options.
在 Category 列表, 点击 Security and Trust.
在 Security Level , 清除 Automatically determine security level.
选择 Full Trust, 然后点击 OK.
