my iPhone OpenGL ES application receives touch events after a delay, why?

I'm developing a game on the iPhone, using OpenGL ES 1.x to render stuff.

It seems that my OpenGL ES view receives touch events after a noticeable delay on some iPhone devices, and on some other devices the touch events are received immediately... all the iPhone devices I have been testing my SW with have iOS 4 installed.

By some googling I noticed that at least UIScrollView (or something) has a delayCon开发者_开发问答tentTouches property, but that doesn't quite apply as I only have the GL view controller in my app.

I also added some code to NSLog the time between receiving the touch event and the next screen refresh and the delay is well below the time between screen refreshes. The app doesn't apparently hog the CPU, either, as the frame rate is constantly around 60fps.