Razr: unable to charge via usb

I bought a sweet charger kit at Radioshack the other day. It has a prong that plugs in to the wall and the other end is female USB port. You can plug USB stuff in there(Ipod cable, Razr cord, whatever) and charge things.

Unfortunately, it won't charge my phone using a regular USB cable, it just says "unable to charge" yet it turned the phone on.

What gives here?
Same thing applies the kit using the car plug +usb cable to Razr.

for the computer, you need to have some "drivers" installed so that it will be recognized.