更新扩展数据后保存文件出错

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AcDbDatabase *pDb = new AcDbDatabase(Adesk::kFalse);
  es = pDb->readDwgFile(szDwgFile);
  if (es == Acad::eOk)
  { 
   UnlockAllLayer(pDb);

   pDb->getSymbolTable(pBlkTbl,AcDb::kForRead);
   pBlkTbl->getAt(ACDB_MODEL_SPACE,pBlkTblRcd,AcDb::kForWrite);
   pBlkTbl->close();
   pBlkTblRcd->newIterator(pBlkTblRcdItr);
   for (pBlkTblRcdItr->start();!pBlkTblRcdItr->done();pBlkTblRcdItr->step())
   {
    
    es = pBlkTblRcdItr->getEntity(pEnt,AcDb::kForWrite);
    if (es != Acad.ErrorStatus::eOk)  continue;
    pRb = pEnt->xData("SOUTH");
    if (pRb == NULL)      continue;
    while ((rchain = pRb->rbnext))
    {
     if (rchain->restype == 1000)
     {
      strcpy(szVal,rchain->resval.rstring);
      strcpy(rchain->resval.rstring, "test");
      break;
     }
    }

    es = pEnt->upgradeOpen();
    es = pEnt->setXData(pRb);
    es = pEnt->close();
    acutRelRb(pRb);    
   }
  }
  es = pDb->saveAs("D:\\3.DWG");//(LPTSTR)(LPCTSTR)szCurFilePath//保存出现错误

错误为：文件写入/读出出错