IPhone :: Touch-start Event Not Fired In IOS 4.3?

I used document.addEventListener('touchstart', eventHandler); Evrything works fine in IOS 5, but when it comes to IOS 4.3, touchstart is fired on the entire document except on the input fields.Is there any workaround to make this work on input fields on 4.3 too. I use touchstart because, if i use preventdefault on touchstart handler, it would stop device keypad from popping up (and it does in IOS 5.0) , which isn't happening in 4.3 Obviously.