If you could provide some more details, that might help.
How did you get the g2 maps on a USB stick? did you copy it yourself from the g2 SD card? If so, did you copy all the files and place it in the same folder hierarchy? Which g2 map is this?
What happens in HomePort when you connect the USB stick? Does HomePort detect the USB stick and show it on the top right? If so, does it then show that it is trying to read your map? Does the progress bar for the map become red after some time? If so, when you hover your mouse cursor over the progress bar, do you see any messages?
If you could provide some more details, that might help.
How did you get the g2 maps on a USB stick? did you copy it yourself from the g2 SD card? If so, did you copy all the files and place it in the same folder hierarchy? Which g2 map is this?
What happens in HomePort when you connect the USB stick? Does HomePort detect the USB stick and show it on the top right? If so, does it then show that it is trying to read your map? Does the progress bar for the map become red after some time? If so, when you hover your mouse cursor over the progress bar, do you see any messages?