On the Engadget Show yesterday, Steve Wozniak commented on why the white iPhone has been delayed.
VentureBeat notes that Woz managed to get a hold of white iPhone parts that came from Foxconn. After modding his iPhone 4, Woz noticed that the photos he took looked as though they were taken through cellophane.
Wozniak said that his white iPhone 4 parts caused issues with its proximity sensor (although I think hes actually referring to its ambient light sensor, which could see similar light leakage issues to the camera). He then confirmed that Apple has resolved the problems with the white iPhone 4, and that well be seeing them soon.
A report from Macotakara has also suggested that a new Japanese developed painting material has finally solved the production problems with the white iPhone 4.