cannot access an inactive scope,该如何处理

cannot access an inactive scope
bool __fastcall ComplexFd(int tag,TDBGridEh *Gd,AnsiString &sqlstr,bool &SelAll,bool AllField,bool visID)
{
   bool Ret = false;
   Application->CreateForm(__classid(TfmComplexFd), &fmComplexFd);

   try
   {
       fmComplexFd->CmbFieldName->Items->Clear();
       fmComplexFd->TAG = tag;
       fmComplexFd->edtFrom->Enabled = visID;
       fmComplexFd->edtTo->Enabled = visID;

       ShowMessage(Gd->Columns->Items[0]->Field->DataType);

       for (int i = 0; i < Gd->Columns->Count; i++)
       {
          if((Gd->Columns->Items[i]->Field->DataType != 16)
                && Gd->Columns->Items[i]->FieldName != "EDocNO")
          {
              fmComplexFd->CmbFieldName->Items->Add(Gd->Columns->Items[i]->Title->Caption);                  fmComplexFd->lsSource->AddObject(Gd->Columns->Items[i]->FieldName,(TObject*)Gd->Columns->Items[i]->Field->DataType);

          }
       }
       if(fmComplexFd->ShowModal() == mrOk)
       {
          sqlstr = fmComplexFd->ReturnSQL;
          SelAll = fmComplexFd->SelAll;
          Ret = true;
       }
   }
   __finally
   {
       delete fmComplexFd;
   }
      return Ret;
}

我用ShowMessage去测试，访问Gd->Columns->Items[0]->Field->DataType者一句出错，错误信息是E2208 cannot access an inactive scope 编译不报错，运行才报错。请教大神这是什么原因，我是菜鸟，谢谢了 
[解决办法]
DBGridEh关联的数据集是否处于打开状态？
[解决办法]
DataSource2->DataSet->Fields->Fields->Count
Columns->Count

名字记不清了，大概是这两个属性，你看看是多少，是不是0