I wanted to try Ndrive 3.5.27 on my e51 with an external Bluetooth GPS mouse, but got the dreaded "no fix" although I had 8+ satellites for 30+ minutes.
Time for action!!
I already read that some 15 seconds after switching off the mouse, Ndrive suddenly reported a fix (all green bars in the map display).
Now the trick is to turn on your mouse right at that moment!!!!
Ndrive will pick up the fix from there and get you where you want.
I agree it is not an elegant solution, but it certainly is a work around.