I have an old Nokia phone which charges fine from the adaptor, but refuses to charge using a USB charging cable.
Note that this isn't a normal USB cable, as you can see from the picture, it's got a USB A connector at one end, and a Nokia DC jack at the other.
What's strange is that even if connect this cable to a beefy 5v power supply, the phone still refuses to charge. I know that power is getting through because I can measure the voltage at the phone end of the cable, and the phone seems to notice when I connect the cable, but still won't charge.
Do Nokia phones have some nasty trick they use to prevent unlicensed chargers working with them?