Another day, another iPhone 4 problem in the headlines. But that’s the price Apple pays for launching a must-have phone that has eager punters queuing around the block just to get close to one.

And now those people have got up close and personal with the iPhone 4, they’ve found it’s playing up and developing a mind of its own. Users have complained about unintentionally switching on Apple’s FaceTime video-conferencing and accidental call making.

It’s all down to the proximity sensor, a bit of electronic wizardry that most of us probably aren’t aware of. Instead, we all continue happily in the assumption that when we place our ear close to a touchscreen phone, its screen will magically turn off, and our auricular orifice won’t be responsible for doing the dialling normally performed by our digits.

As with all Apple issues, this one’s all over the web, from the thousands of comments on the Apple support forum, to plenty of YouTube videos alleging to demonstrate the issue.

iPhone 4 vs iPhone 3GS in the labs

But nothing beats a bit of science to confirm (or quash) a rumour, so Which? sent a shiny new iPhone 4 off to its labs for an expert verdict.

Our results showed that the iPhone 3GS deactivated on-screen buttons when we were 55mm from its surface, with the iPhone 4 doing the same at just 40mm – a difference of almost 30%.

We also found that the iPhone 4 took about half-a-second longer than the 3GS to deactivate the screen when it reached its activation range. Remarkable given that Apple has had three previous attempts at making phones that work.

What’s the deal Apple?

Apple has yet to respond to this criticism of its latest iPhone, but some users believe there’s an easy fix – reset your iPhone 4 network settings. Or you could try the advice of an Apple ‘genius’ who claims your ears are at fault… for being too clean.

How Apple will deal with the discord surrounding the iPhone 4’s many problems is currently unknown. But Which? recommends that if it can be fixed with a software update, Apple might be wise to release that very, very soon. There must be a limit to the patience of the millions of gadget lovers who have paid hundreds of pounds for their treasured iPhone 4.