Ok, we've been here before. In fact, we've been here before a good five or six times. But when Apple puts down a release date for the white iPhone 4 on paper, we're saying that's probably a confirmed date. Only probably though.According to 9 to 5 Mac, in the US, signage going up around Apple stores has some interesting news at the bottom. That news claims that the white iPhone 4 is hitting shelves in 'spring 2011'. When is it coming to the UK, you ask? The answer is 'soon after' we suspect, or possibly around the same time. If Apple has mastered the production problems of creating a white iPhone, there's no reason why it can't be knocked out in numbers.The delay is apparently down to paint thickness and the glass screen, the two not working together as they should. We can't work out why white paint is thicker or thinner than black, but it is, if rumours are to be believed.Obviously the arrival of a white iPhone 4 in spring does put a question mark against the expected arrival date of an iPhone 5. Apple refreshes its range on an annual basis, which is also around spring 2011. Would you opt for a white iPhone 4 when a new iPhone 5 is weeks away? Thought not.