Iphone -- Confused about leaks within my NSOperation

My app has an NSOperation class called ServerRequest that handles networking tasks. According to instruments, it is leaking like crazy. Additionally, instruments says the code that builds the request is leaking, even though that is not an NSOperation. But I have followed Apple's advice in terms of setting up an autorelease pool, so I don't understand what could be the matter. Can anyone help?

A portion of my code is below:

-(void) main {
 NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
 self.data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];  // lots of leakage here
 [self postResult]; // leakage here too
 [pool release];
}

and the postResult method (which is not leaking):

-(void) postResult {
// error handling code here

 if (![self isCancelled])
 {
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
  NSMutableDictionary *resultDictionary = [[NSMutableDictionary alloc]init];
  if (self.data!=nil)
   [resultDictionary setOb开发者_StackOverflow中文版ject:self.data forKey:kDataKey];
  if (self.response!=nil)
   [resultDictionary setObject:self.response forKey:kResponseKey];
  if (self.error!=nil)
   [resultDictionary setObject:self.error forKey:kErrorKey];
  NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
  NSNotification *notification = [NSNotification notificationWithName: kDownloadCompleteName object: self userInfo: resultDictionary];
  [resultDictionary release];
  [center postNotification: notification];

  [pool drain];
 }
}

Lastly, dealloc:

- (void) dealloc {
 self.request = nil;
 self.data = nil;
 self.mutableData = nil;
 if (!self.error)
  self.error = nil;
 if (!self.response)
  self.response = nil;
 [super dealloc];
}

Some recommend avoiding the self.var = nil setter approach to releasing variables in the -dealloc deconstructor.

Have you tried the old tried-and-true [var release], var = nil approach?