We are in the process of setting up new CF 10 servers here at work to replace our production CF 9 servers. We have some web services that are used internally to manage our production servers, and I had a devil of a time getting these web services to work. The internal server that needed to talk to the new CF 10 servers runs CF 9. So the troubles were with CF 9 talking to a CF 10 server over web services. I was able to get it mostly working on my own by struggling through things, but then I saw a post on the official ColdFusion Blog that explains how to get around these problems.
As you may remember, ColdFusion 10 features an upgraded web service engine (Axis). ColdFusion 9 had Apache Axis1 while in CF 10 the web services have been upgraded to Axis2. There are compatibility issues because of this upgrade, but ColdFusion has new features to help you handle this. I don’t want to get into the details in this post, but just be aware that if you are having problems between CF 9 and CF 10 web services, check out the link above to solve it.