Q: I have a 40 GB iPod, and when I charge it from the AC adapter, the screen turns blue and is unreadable. But when I charge it from my laptop, via USB2, the screen is normal. Is something wrong?
A: When you charge your iPod from an AC adapter or a FireWire port, it can get very hot. And when the iPod is hot, the screen changes contrast as you describe. Some become very dark and blue when they are hot, but very pale if they are cold. This is “normal.”
Your laptop may not be sending enough power to make the iPod heat up as much as when you have it plugged in to the AC adapter.