Garmin c340 POIloader not responding?

The not responding message is normal, it does it every time when I load POI's. Just wait for the loader to complete and it will tell you it was completed and how many POI's were done.

The target device should be your GPS itself. You should put all the custom POI's you want into one single subdirectory on your computer and select that directory with POI loader. You just select the subdirectory and not the individual files.