Your description sounds like a standard bus-powered circuit as expected, doesn't explain the problem of course. You didn't tell, in which phase of device connection/enumeration the power surgeis detected.
It would be also interesting if it even happens in reset state or without an operational firmware, not enabling the USB interface at all. If it's the case, than only a hardware defect or short circuit could explain the behaviour.
If the overcurrent is detected after regular device enumeration, an incorrect device descriptor may the trivial reason.