Well, because of the low memory warnings someone (the iPhone or instruments) must be wrong. 🙂
So i decided to check if the leaks instrument is wrong and looked for a different instrument to check the overall memory allocation of my app.
I found the memory monitor instrument which show the memory usage for alle the processes running on the device.
I than just repeated some specific funktions of my app and checked the memory usage of my app.
In my case for example i found a leak in my implementation of
- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view
where i forgott to autorelease the returned view. This way i "lost" a UIView each time a new one was created for the UIPickewView. And the leaks instrument was not aware of that.