The problem may be one of the ports not being able to power both devices at once, although I think they are on separate USB buses and should be able to do so. Or the problem may be a simple physical one of the ports being too close together for both plugs to fit in side-by-side.
In either case, a USB hub with its own AC adapter may be a solution. If each port will power each device separately, but it's essential to plug both devices in at the same time when AC power is not available, connecting one of them via a [USB extension cable|http://www.amazon.com/Inch-Fully-Rated-Extension-Cable/dp/B000E5CYW8] (with a smaller plug than the one on the device itself) may suffice. I have such a cable and sometimes use it because of its smaller plug, even though I don't need its extra length. Of course if extra length would sometimes be handy, such cables are available in many different lengths.
