More power, Scottie!
Bottom line... get an external power adaptor (5 VDC, 1.0 A).
I had same problem with my PowerBook G4 and SimpleTech PininFarina 120GB. I purchased a "Universal AC/DC Adaptor" made by some company called XG for $20. US.
The thing that confused me most was that the MAC saw the device, but not the volume. That is, with both the Data/Power and Power-Only USB plugs connected for more power per the instructions (Quick Start guide, a PDF available from their Tech Support site), the System Profiler saw that there was a storage device attached, but the volume did not load and the system did not see the files and directories on it.
Also, the red power light on the drive comes on, but the blue data-read light never shows. This seems to mean there is not enough power to actually run the drive. You can only tell the drive is actually working by the whirring sound it makes, which you would not know since you have not heard it yet.
I was able to figure this out only because I got a new MacMini, and having forgotten the SimpleTech drive did not work on the PowerBook G4, I hooked it up to the Mini and it accessed with no problem. I had earlier thought it was a drive format issue, but once I got it on the MacMini, I was able to format the drive just as the documentation describes.
The power adaptor I got can be switched for different voltages, and had a range of connectors, which included the right size for the SimpleTech. The connectors are separate pieces and attach to a cable coming from the adaptor. The connectors and cable are poorly marked and reversible, so figuring out polarity without risking the drive was a challenge. I used a USB hub I had handy, which had an LED in it. If the LED lit, I knew I had the power supply connector on the cable correctly. The important thing is the power supply be switchable to 5 VDC. My power supply is rated at 2500mA (2.5 Amp), and the drive only draws 1 Amp of current.
I hope this helps.
/Frank.
