Yes, in theory any USB keyboard should work via the camera connection kit, without knowing more about your setup it's hard to know what the problem is - potentially have to change settings on the keyboard to make it output it's midi data?
For those people who have controllers which are true midi, not USB, there's the IK Multimedia iRig MIDI that's just launched - same guys who produce the iRig for guitars, this is a midi adapter that let's you control synth apps etc.
Hi incapete,
I had a look through the manual and it has settings that can be changed but I don't know how relevant they are. So now I've sent a message directly to Casio's support section and hope they might provide me with an answer.