This blog entry at the CEntrance site says that they conducted a survey, determining that the typical USB port can deliver 500mA at 5V.
They then designed the DACport to start out drawing only 60 mA, but during normal operation it demands no more than 400 mA.
These numbers are for their DACport, which has a both a DAC and a headphone amplifier.
I would imagine that their DACport LX (the device I reviewed) must therefore have a peak demand of something less than 400 mA (given that it's just the DAC, without the amplifier.)
Do you have an ODAC and, if so, is it exhibiting symptoms similar to what I described in my review?