Access violation Access violation at address 00448A07 in module ExpDataFromAD.exe. Read of address 00000000

CoInitializeEx(nil, COINIT_MULTITHREADED);

  try
    try
      vAdoConn:=TADOConnection.Create(nil);
      vAdoConn.LoginPrompt:=false;

      vAdoConn.ConnectionString:='Provider=ADsDSOObject;Password='+aPassword+';User ID='+aLogin+';Encrypt Password=False;Mode=Read';
      vAdoConn.Open;
    except
      on e:exception do
      begin
        WriteLog(vErrorFile, 'Export PC List from AD error: '+e.message);
        exit;
      end;
    end;

    try
      vAdoQuery:=TADOQuery.Create(nil);
      vAdoQuery.Connection:=vAdoConn;

      LastDate:= now - 15;
      vObjectName:='computer';
      vSQL:='select Name, operatingsystem, operatingSystemVersion, objectguid, useraccountcontrol, whenCreated, distinguishedName '+
            'from '+quotedstr('LDAP://'+vDomainName)+' where objectClass='+quotedstr(vObjectName);
      vSQL:= vSQL + ' and whenCreated > '+ quotedstr(GetDTString(LastDate)); 

      vAdoQuery.Close;
      vAdoQuery.SQL.Text:=vSQL;
      vAdoQuery.Open;
      if NOT vAdoQuery.IsEmpty then //exit;
      begin
        setlength(PCMas, vAdoQuery.RecordCount);
        vAdoQuery.First;
        j:= 0;
        while not vAdoQuery.eof do
        //for j:= 0 to vAdoQuery.RecordCount-1 do
        begin
          for i:= 0 to vAdoQuery.FieldCount-1 do
          begin
            vFieldVal:=vAdoQuery.Fields[i].AsString;

            if vAdoQuery.Fields[i].FieldName='Name' then
              PCMas[j].PCName:= vFieldVal;
          end;

          vAdoQuery.Next;
          inc(j);       
        end;
      end;      

      vAdoQuery.Close;
    except
      on e:exception do
      begin
        WriteLog(vErrorFile, 'Export PC List from AD vAdoQuery execute error: '+e.message);
      end;
    end;
  finally
    if (vAdoQuery <> nil) then vAdoQuery.Free;
    vAdoConn.Free;
  end;

while not vAdoQuery.eof do

procedure TForm1.Button1Click(Sender: TObject);
var
  NewPCMas: TNewPCMas;  
  LastCheckTime: Tdatetime;
  aLogin, aPassword: string;
begin
  LastCheckTime:= Now-2190;
  aLogin:= 'domain\testuser';
  aPassword:= 'userpassword';

  GetNewPCFromAD(LastCheckTime, aLogin, aPassword, NewPCMas);
end;