Hi David,
Can you test with the latest bits? I did some work just before the v0.7 release and I think this should be working now. I was able to reproduce the problem yesterday, moved some logic around and it did work in my tests.*
It's an unfortunately complicated piece of logic and it was a long day, so if there's still problems we'll keep working on it till its 100%.*
That said, there still may be problems if posting to url that ends in a "/" or no file extension.*
You could also try setting Method="GET" on the AjaxEvent/AjaxMethod.
Hope this helps.