I'm now on Windows 8.1 64bit running X3b 64bit. I've correctly set up the Faderport so that the Faderport can be selected from the list of control surfaces. However, only the fader seems to send any info to Sonar - all the buttons don't work. They do receive input from Sonar correctly, if I start or stop the transport using the mouse, the correct button lights up on the Faderport, for example. 
 
Anybody else have this issue?

Well I just fixed it myself about three minutes after posting this thread! I forgot to check the aftertouch settings in MIDI options - I did that now it's all working as it should!
 
Thank you me! :)

Thank you for solving this and thanks google search function for finding this for me.  I would have been digging for a while....