Seems that this is also true for simple asp.net web services and not only WCF.
Careful as the global.asax is in a "<script"> tag environment but basically it's the same code.
I had to enable the post and get commands in web.config but that can be found in the server event viewer when you get something as a "URL cannot be resolved" error, the domain issue will not be written to event viewer as I can observe.