If it works in a 2nd computer and not this one, then:
USB1/2 have a current limit of 0.5Amps (only 2.5 Watts available). This current limiting circuit could have been damaged and now is going into current limiting at a lower current.
Normally this problem is hardware assosicated and not user repairable.
The new USB standard will up this from 0.5Amps to I believe 1.8Amps.