I do wonder about a similar problem I've had, though. If I make one element transparent (not grouped or anything, definitely just the one item), sometimes other elements on the page shift colors. The item I'm changes doesn't overlap the others or anything, and it not only affects the screen display but the printout as well. It's almost as though ID is changing how it calculates colors or something.
Is this a known issue? (This is all with ID 2, btw.)