The only difference that I can tell is that the G4 ibook has USB 2.0 (which the GPS mouse is listed as supporting, but even if it didn't, USB is backwards compatible.)
The device itself has a 9 pin DIN connector plugged into the DIN->USB adaptor.
The issue specifically is that when plugged in, the device does not show up any device list from within KisMAC and Macstumbler. After pludding around /dev, I'm thoroughly sure the device is not operating.
This is the device:
http://cgi.ebay.com/ws/eBayISAPI.dll...MEWN%3AIT&rd=1
Anyone have any experience with this sort of problem?