Midi Keyboard AKAI professional LPK25 not showing in 'Choose PortMidi input interface'

Hi and thanks in advance. MuseScore is incredible....

MuseScore 1.1
Windows 7
New Computer
Akai Professional KPK25 Laptop performance Keyboard (25 keys); USB - MIDI controller

Works fine when I use it with Reaper. The keyboard is detected and listed by my computer as an 'audio device'.

1. open MuseScore
2. start new project instruments ...
3. depress 'enable midi input' (near the play button)
4. Edit; Preferences; I/O; Choose PortMidi input interface
5. There is nothing in the drop down box

Any suggestions? I am writing for drum kit, so having the keyboard working is essential!

Regards,

Stu