I installed a pc into a car a few years ago and had trouble with the hubs not allowing things to be "seen" properly like this .
It turned out in my case to be a power problem when splitting the usb's via the hubs on an "efficient" (read low) power computer .
When i got some hubs that had there own seperate power supply it all ran smoothly . Being a laptop its just a possibility that its a low power issue here too as theres not too much grunt behind those connections and gps can get hungry i believe .
Not too likely but its possible .
PS post count of one ! wheeeee.
