ayuda comprobando campos

[jonydread]

me pueden ayudar porfavor tengo esto pero me aparece un error de access violation

Código Delphi [-]
procedure TForm2.BitBtn11Click(Sender: TObject);
var
cItem: TListItem;
id,man: string;
i: integer;
begin
if (dblookupcombobox1.KeyValue = NULL) or (edit11.Text='') or (edit12.Text='') then
begin
MessageDlg('complete campos', mtWarning, [mbOk],0);
Abort;
end
else
if ListView5.Items.Count > 0 then
for i:= 0 to Listview5.Items.Count -1 do
begin
if Pos('cadena', Listview5.Items[i].Caption) <> 0 then
begin
MessageDlg('ya existe elemento', mtWarning, [mbCancel],0);
Abort;
end else
begin
  man:= uman.Text;
  Zquery1.sql.text := 'insert into MP values (:area,:id,:elemento,:frecuencia,:tipo,:umant,mant)';
  ZQuery1.ParamByName('area').AsString := label8.Caption;
  ZQuery1.ParamByName('id').AsString := dblookupcombobox1.KeyValue;
  ZQuery1.ParamByName('elemento').AsString := dblookupcombobox1.Text;
  ZQuery1.ParamByName('frecuencia').AsString := edit11.Text;
  ZQuery1.ParamByName('tipo').AsString := edit12.Text;
  ZQuery1.ParamByName('umant').AsString := man;
  ZQuery1.ParamByName('pmant').AsDate := Datetimepicker4.Date;
  ZQuery1.ExecSQL;
  zQuery1.SQL.Clear;
  Zquery1.Close;
  Listview5.Clear;
end end else
begin
  man:= uman.Text;
  Zquery1.sql.text := 'insert into MP values (:area,:id,:elemento,:frecuencia,:tipo,:umant,mant)';
  ZQuery1.ParamByName('area').AsString := label8.Caption;
  ZQuery1.ParamByName('id').AsString := dblookupcombobox1.KeyValue;
  ZQuery1.ParamByName('elemento').AsString := dblookupcombobox1.Text;
  ZQuery1.ParamByName('frecuencia').AsString := edit11.Text;
  ZQuery1.ParamByName('tipo').AsString := edit12.Text;
  ZQuery1.ParamByName('umant').AsString := man;
  ZQuery1.ParamByName('pmant').AsDate := Datetimepicker4.Date;
  ZQuery1.ExecSQL;
  zQuery1.SQL.Clear;
  Zquery1.Close;
  Listview5.Clear;
end;

  Zquery1.SQL.Text := 'SELECT * From MP where area = :area';
  zQuery1.ParamByName('area').AsString:= label8.Caption;
  zquery1.Open;
while not zquery1.Eof do
begin
cItem := Listview5.Items.Add;
cItem.Caption := zQuery1.fieldbyname('id').AsString;
cItem.SubItems.Add(zQuery1.fieldbyname('elemento').AsString);
cItem.SubItems.Add(zQuery1.fieldbyname('frecuencia').AsString);
cItem.SubItems.Add(zQuery1.fieldbyname('tipo').AsString);
cItem.SubItems.Add(zQuery1.fieldbyname('umant').AsString);
cItem.SubItems.Add(zQuery1.fieldbyname('pmant').AsString);
zquery1.next;
end;
edit11.Clear;edit12.Clear;
uman.Clear;
uman.Add('no registra');
Datetimepicker3.Format:= ' ';
end;