Besides its ivory face, very little about the white iPhone 4 has changed in comparison its black predecessor -- except the thickness.

Placing the black and white models side by side, iPhone owners noticed a significant difference in the thickness of the two devices. By some measurements, the white iPhone is 0.2 mm thicker than the original black version. This can be problematic for accessories such as cases, which are built to tight tolerances.

Now some case manufacturers' products won't fit both models of the iPhone. Likewise, users who purchase one of these cases may find that they do not fit their new white device. Some users have noticed that the cases, which no longer fit properly, now interfere with the iPhone's proximity detector, which tells the phone when it is close to your face (and turns off the touch screen in the process).

Apple's decision to increase the thickness of the white iPhone may relate to Apple senior VP Phil Schiller's revelation to Mobilized yesterday that the company faced a number of challenges creating the device. One such difficulty related to the color itself, which caused issues with the iPhone's internal components. Apple didn't opt for simply painting the glass -- the white iPhone's color is a part of the casing. Schiller also noted that the white iPhone, like people with lighter skin, needs its increased protection against ultraviolet light from the sun.