While I've not tried btscanner, yet, on bt4 pre-final, my gut instinct would be that your bluetooth device is not recognized by the kernel when you're running btscanner (driver might not be loaded, etc.) A couple of things to look for:
1.) try turning the bluetooth switch / adapter on before bt4 ever boots, to make sure the OS sees it and tries to initialize it (assuming the proper device drivers are present)
2.) look up the make / model of the bluetooth adapter, and see if it's supported on Linux, and if there are linux device drivers for it.
You could also send us the output from a terminal window, and issuing the lspci command, to see what bt4 sees. You can 'pipe' it to a file, using:
lspci > ~/Desktop/devices.txt
Then copy / paste the output or contents of the file to this list, if you want some of us to see if your hardware is compatible, etc.
~ hayabusa ~
"All men can see these tactics whereby I conquer, but what none can see is the strategy out of which victory is evolved." - Sun Tzu, 'The Art of War'
OSCE, OSCP , GPEN, C|EH