One queer thing is that on many computers, the front and the back ports behave differently. On the one in front of me, you can charge flashlights, phones etc. from the front USB sockets, but not the back- the load has to be a properly responding USB device or it gets no supper. And the back sockets will supply 500mA each, but the front ones only 500mA between them. I suspect it's something to do with USB1/2 changes.

And if USB is bad, what about the sound card connections?