[MSJim]

Round Plug, Round Plug, Round Plug. That's all you need to remember about reader chargers. As long as the voltage of the round plug charger is correct, it will charge the Sony reader. It doesn't matter if the voltage source is a USB car adapter, a USB wall charger, or a cube type wall charger (Sony or PSP type). I actually use a surplus Dell Axim charger. Of course, you must use a cable with a round plug on one end and a USB A plug on the other with the USB wall charger, or USB car adapter. I have a "y" type cable with both round and USB mini plugs on the reader end.
Just don't expect a charge cable, with a mini USB plug on one end and a USB A plug on the other, to charge the reader unless it is connected to a PC, and then only if the PC is active, i.e. not in standby/sleep mode/hibernation/off.
Charging via PC USB ports is generally slower than charging from a round plug equipped wall charger. That's because the wall chargers usually have more current and/or voltage available than the typical USB port.