App crashes in device when images downloaded in ipad?

I am trying to download images which are base64 encoded, they are sending an byte array apended with xml tags, the images size may vary from 2 to 4 mb, iam storing the byte array in a string and then decoding them, in simulator it works fine but when it goes to device, app crashes when download of images completed. I am not getting what happened, if any one knows the techinique please share with me.

Here is my code

// }
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
     [self.receivedData setLength:0];
 }

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
     [self.receivedData appendData:data]; 
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
      [appDelegate hideActivityViewer];
       NSLog(@"Connection failed! Error - %@ %@", [error localizedDescription], [[error userInfo] objectForKey:NSErrorFailingURLStringKey]);
      // [appDelegate hideActivityViewer];
      //open an alert with just an OK button
      UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:[error localizedDescription]
      delegate:nil cancelButtonTitle:@"OK" otherButtonTitles: nil];
      [alert show];
      [alert release];   
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
      [appDelegate hideActivityViewer];
      self.receivedData = nil;
      self.receivedData = nil;
      [handle seekToFileOffset:100];
      [handle readDataToEndOfFile];
      NSString *aStr = [[NSString alloc] initWithData:receivedData encoding:NSASCIIStringEncoding]; 

      NSLog(@"%@",aStr);
      NSString *newString = [aStr stringByReplacingOccurrencesOfString:@开发者_开发知识库"&lt;" withString:@"<"];
      NSLog(@"%@", finString);
      NSXMLParser *xmlPar=[[NSXMLParser alloc] initWithData: (NSData*)receivedData];
     docDwnldPrsr *parser = [[docDwnldPrsr alloc] initXMLParser];
      [xmlPar setDelegate:parser];
     BOOL success = [xmlPar parse];
[aStr release];
self.receivedData = nil;

     if (success){

         if (self.rejectFlag == 1 || self.accptornot == 1) {
             if ( [appDelegate.rejectResult isEqualToString:@"Successful"] && self.rejectFlag == 1) {
                 UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"success" message:@"Aplication rejected successfully" delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil];
                 [alert show];
                 [alert release];
                 self.rejectFlag = 0;
                 appDelegate.rejectResult = @"";
             }
             if ([appDelegate.rejectResult isEqualToString:@"Successful"] && self.accptornot == 1 && self.sigNaturesent == 0) {
                self.rejectFlag = 0;

                 sigNaturesent = 1;

                 NSMutableString *url = [[NSMutableString alloc] init];
                 [url appendString:urlip];
                 [url appendString:@"BSNL_CustomerSignUpload"];

                 NSURL *postUrl = [NSURL URLWithString:url];
                 MultipartForm *form = [[MultipartForm alloc] initWithURL:postUrl cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:20];
                 //[form addFormField:@"SecCode" withStringData:@"N9S8O7F6T5@I4N3D2I1A1"];
                 [form addFile:self.sigImagePath withFieldName:@"docbinaryarray"];
                 NSLog(@"%@", self.sigImagePath);
                 NSMutableURLRequest *postRequest = [form mpfRequest] ;

                 NSLog(urlip);
                 //[url release];
                 [urlip release];

                 NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:postRequest delegate:self];
                 if (theConnection) {

                     self.receivedData=[NSMutableData data];

                 }
                 else {

                     NSLog(@"Failed");

                 }
                 [form release];
                 [theConnection release];   
             appDelegate.rejectResult = @"";
             }
             else if ([appDelegate.rejectResult isEqualToString:@"Successful"] && self.sigNaturesent == 1) {
                 UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"success" message:@"Aplication accepted successfully" delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil];
                 [alert show];
                 [alert release];
                 self.sigNaturesent = 0;
             }
         }
         else { 
        // decoding of images starts here
         Byte inputData[[appDelegate.documentsImagesString lengthOfBytesUsingEncoding:NSUTF8StringEncoding]];
         [[appDelegate.documentsImagesString dataUsingEncoding:NSUTF8StringEncoding] getBytes:inputData];
         size_t inputDataSize = (size_t)[appDelegate.documentsImagesString  length];
         size_t outputDataSize = EstimateBas64DecodedDataSize(inputDataSize);
         Byte outputData[outputDataSize];
         Base64DecodeData(inputData, inputDataSize, outputData, &outputDataSize);
         NSData *theData = [[NSData alloc] initWithBytes:outputData length:outputDataSize];
         NSArray *paths= NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
         NSString *path = [paths objectAtIndex:0];
         NSString *filePath = [path stringByAppendingPathComponent:@"data.zip"];    
         NSLog(filePath);
             appDelegate.documentsImagesString = nil;
          NSFileManager *fm = [NSFileManager defaultManager];
         [fm removeItemAtPath:[NSString stringWithFormat:@"%@/data",path] error:nil];
         [theData writeToFile:filePath atomically:YES];
             [theData release];
         NSString *zip = [path stringByAppendingPathComponent:@"data"];
         [fm createDirectoryAtPath:zip attributes:nil];
         ZipArchive *unZip = [[ZipArchive alloc] init];
         [unZip UnzipOpenFile:filePath];
          [unZip UnzipFileTo:zip overWrite:YES];
         [unZip UnzipCloseFile];
        NSArray *arr = [fm subpathsAtPath:zip];
         appDelegate.paths = arr;
         NSMutableArray *temp = [[NSMutableArray alloc] init];
         appDelegate.imagesData = temp;
         [temp release];
        [fm removeItemAtPath:filePath error:nil];

         NSLog(@"the end");
         appDelegate.path1 = zip;
        // NSString *recData = [self decodeBase64:appDelegate.documentsImagesString];
        // [recData writeToFile:@"/Users/madhukar/Desktop/data.txt" atomically:YES];
         [appDelegate.imagesData addObject:[UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/%@",zip, [arr objectAtIndex:1]]]];
         [appDelegate hideActivityViewer];
         self.docViewFlag = 1;
         [self toggleDocumentsList:self];

     }

     }



 }

please dont consider comments thanks Kumar