Creating A New Thread Results In Autorelease Memory Leaks

I have used the following code to create a new thread:

[NSThread detachNewThreadSelector:@selector(backgroundMethod:) 
                                             toTarget:self 
                                             withObject:paramObject];

And then in backgroundMethod I have set up a new autorelease pool as per usual:

-(void)backgroundMethod:(id)parameter
{
   NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

   //method stuff here...

  [pool drain];
}

But somehow the autorelease pool is not working. When running the code, the output in the console is as follows:

2011-02-17 00:38:16.928 audioEngine[13670:af03] *** __NSAutoreleaseNoPool(): Object
0x4b22370 of class NSThread autoreleased with no pool in place - just leaking

I have used multiple threads in the same way before and had no similar problem - what am I doing wrong?

Any help is much appreciated! Thanks :)

EDIT: Ok this seems a bit weird - I created an autorelease pool in the method that the new thread is created from, and the problem disappeared. Any idea as to why this might be and what the right way to fix it should be? I'd rather not have a random autorelease pool in my code without knowing what it's actually doing and why the problem is gone.

EDIT2: Here's the code creating the main autorelease pool:

int main(int argc, char *argv[]) {

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    int retVal = 开发者_开发技巧UIApplicationMain(argc, argv, nil, nil);
    [pool release];
    return retVal;
}

It seems that it's complaining that the detachNewThreadSelector: call is the one that isn't being made with an autorelease pool in place, and not something within the backgroundMethod function, so that when the backgroundMethod finishes executing, the thread object is being leaked.

Check that the thread (main thread) that creates the background thread has an autorelease pool set up.