Purely out of interest anyone know what in the production process could be causing this?

"Engadget is reporting that the “manufacturing difficulties” lie with the Chinese manufacturer, Lens Technology, the glass manufacturer responsible for the iPhone touchscreen touchscreen. The Chinese manufacturer handles all aspects of the glass manufacturing, from the cutting of the raw material, to screen printing, to the anti shatter treatments. According to the report, a Lens Technology employee is claiming that the delay is a result of a problem with the screen-printing. Specifically, there have been issues in attempting to find the perfect combination of paint thickness and opacity. The paint thickness ensures that the next sub-contractor has room for the digitizer overlay, while the opacity is required to get the exact level of whiteness that Apple wants."

According to an anonymous Gizmodo reader here [ http://gizmodo.com/5570963/apple-white-iphones-more-challeng... (see update 2)] the display glass is not painted but screen printed, presumably so it can be translucent for the sensors beneath it. It seems that Apple want to achieve both the required translucency and an even, saturated white, which is quite tricky.