I've got a button the user tap to start recording and tap again to stop. When it stop I want the recorded voice 'echo' back so the user can hear what was recorded. This works fine the first time. If I hit the button for the third time, it starts a new recording and when I hit stop it crashes with EXC_BAD_ACCESS.

- (IBAction) readToMeTapped {

        if(recording)

        {
        recording = NO;
        [readToMeButton setTitle:@"Stop Recording" forState: UIControlStateNormal ];    

        NSMutableDictionary *recordSetting = [[NSDictionary alloc] initWithObjectsAndKeys:
         [NSNumber numberWithFloat: 44100.0],                 AVSampleRateKey,
         [NSNumber numberWithInt: kAudioFormatAppleLossless], AVFormatIDKey,
         [NSNumber numberWithInt: 1],                         AVNumberOfChannelsKey,
         [NSNumber numberWithInt: AVAudioQualityMax],         AVEncoderAudioQualityKey,
         nil];

        // Create a new dated file
        NSDate *now = [NSDate dateWithTimeIntervalSinceNow:0];
        NSString *caldate = [now description];          
        recordedTmpFile = [NSURL fileURLWithPath:[[NSString stringWithFormat:@"%@/%@.caf", DOCUMENTS_FOLDER, caldate] retain]];
        error = nil;
        recorder = [[ AVAudioRecorder alloc] initWithURL:recordedTmpFile settings:recordSetting error:&error];
        if(!recorder){
            NSLog(@"recorder: %@ %d %@", [error domain], [error code], [[error userInfo] description]);
            UIAlertView *alert =
            [[UIAlertView alloc] initWithTitle: @"Warning"
                                       message: [error localizedDescription]
                                      delegate: nil
                             cancelButtonTitle:@"OK"
                             otherButtonTitles:nil];
            [alert show];
            [alert release];
            return;
        }


        NSLog(@"Using File called: %@",recordedTmpFile);
        //Setup the recorder to use this file and record to it.

        [recorder setDelegate:self];
        [recorder prepareToRecord];

        [recorder recordForDuration:(NSTimeInterval) 5]; //recording for a limited time

    }
    else
    { // it crashes the second time it gets here!
        recording = YES;            
        NSLog(@"Recording YES Using File called: %@",recordedTmpFile);
        [readToMeButton setTitle:@"Start Recording" forState:UIControlStateNormal ];

        [recorder stop]; //Stop the recorder.

        //playback recording
        AVAudioPlayer * newPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:recordedTmpFile error:&error];
        [recordedTmpFile release];

        self.aPlayer = newPlayer;
        [newPlayer release];

        [aPlayer setDelegate:self];
        [aPlayer prepareToPlay];
        [aPlayer play];
        }   
}

- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)sender successfully:(BOOL)flag {

        NSLog (@"audioRecorderDidFinishRecording:successfully:");

        [recorder release];
        recorder = nil;
}

Checking the debugger, it flags the error here

@synthesize aPlayer, recorder;

This is the part I don't understand. I thought it may have something to do with releasing memory but I've been careful. Have I missed something?