帮忙看下这段代码错在哪?(indy，idtcpserver)

主要是同时下线的问题，同时下线时出错，无法发出下线的命令，我知道问题是出在将pclient设为全局变量上，但我用了，EnterCriticalSection(cs);LeaveCriticalSection(cs)了，怎么还不行呢？（我知道ＶＣＬ是非安全的，在我的完整程序里有考虑到了，这个不是主要的问题）Private
     pclient:array of Rclientdata;
      
    { Private declarations }
  public     cs: TRTLCriticalSection;
    { Public declarations }
  end;var
  Main: TMain;
implementation{$R *.dfm}
procedure TMain.FormShow(Sender: TObject);
begin
 idtcpserver1.Active:=true;
 dm.ADOConnection1.Connected:=true;
 dm.userQuery.Active:=true;
 dm.machineQuery.Active:=true;
 InitializeCriticalSection(cs);
 rzrichedit3.Lines.Add('服务器已激活，欢迎使用本软件');
end;procedure TMain.IdTCPServer1Execute(AThread: TIdPeerThread);
var
msg:RmessageData;
rec,rec1,rec2,rec3,rec4,rec5:RrectiveData;i:integer;
begin
  if not athread.Terminated then
  begin
    athread.Connection.ReadBuffer(msg,sizeof(msg));
     EnterCriticalSection(cs); 
try
    case msg.command of
  
    clogin:
    begin      with listbox1 do
       if items.IndexOf(msg.userName)>-1 then
       begin        rec3.command:=cloginError;
        athread.Connection.WriteBuffer(rec3,sizeof(rec3));
       end
       else
        begin
          dm.userQuery.Close;
          dm.userQuery.SQL.Clear;
          dm.userQuery.SQL.Add('select * from userMessage where Name= "'+msg.userName+ '" and Password= "'+msg.password+'"');
          dm.userQuery.Open;
          if not dm.userQuery.Eof then  //将登录信息写入数据库
          begin
            dm.machineQuery.Append;
            dm.machineQuery.FieldByName('UserName').AsString:=msg.userName;
            dm.machineQuery.FieldByName('IP').AsString:=msg.IP;
            dm.machineQuery.FieldByName('Port').AsString:=msg.port;
            dm.machineQuery.FieldByName('StartTime').AsDateTime:=now();
            dm.machineQuery.Post;            rec.command:=cloginOK;
            rec.userName:=msg.userName;
            athread.Connection.WriteBuffer(rec,sizeof(rec));             for i:=0 to high(pclient) do
             begin
               rec1.command:=cuserList;
               rec1.userName:=pclient[i].username;
               rec2.command:=cuserList;
               rec2.userName:=msg.userName;
               pclient[i].thread.Connection.WriteBuffer(rec2,sizeof(rec2));
               athread.Connection.WriteBuffer(rec1,sizeof(rec1));
             end;
             setlength(pclient,high(pclient)+2);
             pclient[high(pclient)].username:=msg.userName;
             pclient[high(pclient)].thread:=athread;             Items.Add(msg.userName);
             rzrichedit3.Lines.Add('用户   '+msg.userName+'   上线了');          end
          else
        begin
          rec3.command:=cloginError;
          athread.Connection.WriteBuffer(rec3,sizeof(rec3));
        end;
        end;      //end;    end;
       coffOnline:
    begin      for i:= high(pclient) downto 0 do
      begin
        if pclient[i].username=msg.userName then
        begin
         pclient[i]:=pclient[high(pclient)];
         setlength(pclient,high(pclient));
         //break;
        end;
      end;
      
      for i:=high(pclient) downto 0 do
      begin
        rec5.command:=cdeleOnline;
        rec5.userName:=msg.userName;
        pclient[i].thread.Connection.WriteBuffer(rec5,sizeof(rec5));
        rzrichedit1.Lines.Add(pclient[i].username);
      end;
     
       with listbox1.items do
       if IndexOf(msg.userName)>-1 then
       begin
         Delete(IndexOf(msg.userName));
       end;
       rzrichedit3.Lines.Add('用户 '+' '+msg.userName+'  下线了') ;    end;  end;
  finally
    LeaveCriticalSection(cs);
  end;
 
  end;
end;end.
主要是同时下线的问题，同时下线时出错，无法发出下线的命令，我知道问题是出在将pclient设为全局变量上，但我用了，EnterCriticalSection(cs);LeaveCriticalSection(cs)了，怎么还不行呢？（我知道ＶＣＬ是非安全的，在我的完整程序里有考虑到了，这个不是主要的问题）
说明
pclient:array of Rclientdata;RclientData=record
    username:string[20];
    thread:TIdPeerThread;