iOS Memory leaks

Hi all,
- (UITableViewCell *)tableViewUITableView *)tableView cellForRowAtIndexPathNSIndexPath *)indexPath
{
NSString *MyIdentifier = @"MyIdentifier";

UITableViewCell *cell = (UITableViewCell *)[tableView dequeueReusableCellWithIdentifier:MyIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:MyIdentifier]autorelease];
}


//UITableViewCell *cell = [[UITableViewCell alloc]init];

itemObject = nil;
itemObject = [menuObject.menuItemsArray objectAtIndex:indexPath.row];
cell.text = itemObject.itemName;
cell.font = [UIFont systemFontOfSize:13.0];
cell.textColor = [UIColor blackColor];
cell.textAlignment = UITextAlignmentLeft;

if(itemObject.iImg != nil)
{

if([[itemObject.iImg substringToIndex:4] isEqualToString"http"])
{
//NSAutoreleasePool *poolObj = [[NSAutoreleasePool alloc]init];
NSURL *urlString = [[NSURL alloc]initWithString:itemObject.iImg];
NSData *data = [[NSData alloc]initWithContentsOfURL:urlString];
UIImage *img = [[UIImage alloc]initWithData:data];
cell.image = img; //[UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:itemObject.iImg]]];
img = nil;
data = nil;
urlString = nil;
itemObject = nil;
//[poolObj drain];

}
else
{

cell.image = [UIImage imageNamed:itemObject.iImg];
}

state = 1;
}


//[itemObject release];

return cell;

}
when i run my app,i see leaks in my instruments and when we trace the stack it will go to this line.
NSData *data = [[NSData alloc]initWithContentsOfURL:urlString];
i am not able to find it out why.so please help me.

Not only here,i am parsong xml files using NSXMLParser object,it will show me leaks at this line also
NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL:URL];
i am relesing parser object.



- (void)parseXMLFileAtURLNSURL *)URL parseErrorNSError **)error
{
//[self parseXMLFileAtData:[NSData dataWithContentsOfURL:URL options:1 error:error]];
NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL:URL];

// Set self as the delegate of the parser so that it will receive the parser delegate methods callbacks.
[parser setDelegate:self];
// Depending on the XML document you're parsing, you may want to enable these features of NSXMLParser.
[parser setShouldProcessNamespaces:NO];
[parser setShouldReportNamespacePrefixes:NO];
[parser setShouldResolveExternalEntities:NO];

[parser parse];

NSError *parseError = [parser parserError];
if (parseError && error)
{
*error = parseError;
}

[parser release];
}

ya, i have released the obj by calling release on them.But still there is leak showing for this line.
NSData *data = [[NSData alloc]initWithContentsOfURL:urlString];

Hi ,most recent code is here

NSURL *urlString = [[NSURL alloc]initWithString:itemObject.iImg];
NSData *data = [[NSData alloc]initWithContentsOfURL:urlString];
[urlString release];
UIImage *img = [[UIImage alloc]initWithData:data];
[data release];
cell.image = img;
[img release];


it is showing leak at this line
NSData *data = [[NSData alloc]initWithContentsOfURL:urlString];

even if i replace the above code with the following it shows the leak for the following line.
cell.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:itemObject.iImg]]];