USB flash drive not shown
When "System Report" aka "System Profiler" does not list your USB devices, and Windows running from Boot Camp also does not list your USB devices and no power is supplied by your USB devices it is very likely that this is not a software issue.

Another way to see your connected USB devices with detailed information is to run

system_profiler SPUSBDataType


If the above fails and gives no satisfied output, it is very, very likely some of your internal hardware components are broken or disconnected.

When there are no problems with your other IO devices (e.g. firewire) it might be an internal cable that came lose, else I would suggest your south bridge is broken.

If you still think the power is the problem, try to use a powered-USB hub that will provide the juice needed for your peripherals. Or you can try to plug-in a low power consuming device like a USB mouse.