Confusing automation behaviour

I create a new project, load session drummer, route that to a bus and insert CamelPhat in that bus.  Then if I click write enable in the CamelPhat interface and turn it on & off / move controls whilst Sonar is playing, the automation information is generated for that bus, for any and all controls I change.
 
If I do exactly the same in the project I am working on (i.e. put CamelPhat on the drums bus, enable write automation, move controls whilst Sonar is playing), no automation information is generated.  I can't get write automation to work no matter what I do in my project, the only option I can get to work is to draw it all in by hand.
 
Any idea what the difference might be?  I've been comparing the two projects side by side for like an hour now and can't see why one is working and the other isn't.