Hi this has started to happen to me recently, working across indesign and photoshop, for some cutouts it is easier to have a "pure white" background (0%c, 0%m, 0%y, 0%k) rather than transparancy, it keeps down file sizes and speeds up workflow etc - plus sometimes press images just come like that.
recently I have noticed that some images, despite being saved as a "pure white" background, are coming out with 1%c, 1%m, 1%y, 0%k backgrounds once I re-open them. Does't matter if I save, Save as, copy the image, duplicate it, I keep getting the 1% colour back in. This is occasionally causing problems with printers.
any tips?