Can the touch screen on iPhone 3G be changed to sensitivity? This is annoying when scrolling.
Is your iPhone jailbroken? There are some fixes out there if it is - like this one - http://limitededitioniphone.com/iphone-touchscreen-fix-increase-sensitivity/
But I haven't tried it myself so I can't vouch for it or what it would do to your phone. But if your phone isn't jailbroken, chances are there isn't much you can do about it.