FTP 下载有时候会提示文件不存在

  m_LocalFileName = GetPath(recordtime.ToShortDateString(), agentName, agentid, m_FolderBrowserDialog.SelectedPath) + "\\" + FileName;                                m_RemoteFileName = AppConfig.ReadConfig("RecRemoteFolder").Trim() + Recordpath;
                                //  string m_RemoteFileName = m_RecDetail.RecordPath;                                               if (m_FtpClient.Exists(m_RemoteFileName))
                                {
                                    m_FtpClient.Download(m_LocalFileName, m_RemoteFileName);
                                    okCount++;
                                }
                                else
                                {
                                    errorString += string.Format(" 第{0}页第{1}下载[{2}]不存在,请检查 \r\n ", j + 1, i, m_RemoteFileName);
                                    isErrorExist = true;
                                }用的类库就是那个edtftpnet.dll
下载的时候有时候可以，但有时候会报文件不存在，但是到ftp服务器上去看了，发现文件确实是存在的。有没有哪位大侠告诉一下这是怎么回事？