post the code in you login view controller. Most of the times a single error message like that isnt very helpful in diagnosing a problem. Its easier to figure out when you have some context (your code, a stack trace, etc)

// // LoginViewController.m // Ribbit // // Created by Blake Mitchell on 12/4/13. // Copyright (c) 2013 Blake Mitchell. All rights reserved. //

import "LoginViewController.h"

import <Parse/Parse.h>

@interface LoginViewController ()

@end

@implementation LoginViewController

• (void)viewDidLoad { [super viewDidLoad];

  self.navigationItem.hidesBackButton = YES; }

• (IBAction)login:(id)sender { NSString *username = [self.usernameField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *password = [self.passwordField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

  if ([username length] == 0 || [password length] == 0) { UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Oops!" message:@"Make sure you enter a username and password!" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alertView show]; } else {

  [PFUser logInWithUsernameInBackground:username password:password block:^(PFUser *user, NSError *error) {
      if (error) {
          UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Sorry!"
                                                              message:[error.userInfo objectForKey:@"error"]
                                                             delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
          [alertView show];
      }
      else {
          [self.navigationController popToRootViewControllerAnimated:YES];
      }
  }];
  

  } }

@end