issue with EXC_BAD_REQUEST in TWRequest

I have the following code and it always gives me a crash when performing the request, any idea?

NSString *responseBody = [[NSString alloc] initWithData:data
                                                       encoding:NSUTF8StringEncoding];

        NSLog(@"Response body is %@", responseBody);

        NSDictionary *accessTokenRequestParams = [[NSMutableDictionary alloc] init];
        [accessTokenRequestParams setValue:CONSUMER_KEY forKey:@"x_reverse_auth_target"];
        [accessTokenRequestParams setValue:responseBody forKey:@"x_reverse_auth_parameters"];            

        NSURL *url2 = [NSURL URLWithString:@"https://api.twitter.com/oauth/access_token"];
        TWRequest * accessTokenRequest = [[TWRequest alloc] initWithURL:url2 parameters:accessTokenRequestParams requestMethod:TWRequestMethodPOST];


        if (selectionIndex != -1)
            [accessTokenRequest setAccount:[self.twitterACAccounts objectAtIndex:selectionIndex]];

        // execute the request
        [accessTokenRequest performRequestWithHandler:
         ^(NSData *responseData, NSHTTPURLResponse *urlResponse, NSError *error) {
             NSString *responseStr = 
             [[NSString alloc] initWithData:responseData 
                                   encoding:NSUTF8StringEncoding];

            NSLog(@"The user's info for your server:\n%@", responseStr);
         }];

UPDATE: Turning on NSZombieEnabled gives me

*** -[ACAccountStore typeForAccount:]: message sent to deallocated instance 0x7199c70

this is no where to be found

Your error looks completely different than your question. You have error in ACAccountStore class. Check your retain count when you accessing, manipulating, and store accounts (ACAccountStore). I think you are deallocated memory first and you are using some where.