Arthur,
As there have been quite a number of updates on the xml mapping engine in the platform it might be that the service is not yet compatible with the latest version of Mendix. The last release was September 2015. Did you try and import the service in a earlier version?
I gave the import of the service a try in Mx 6.2 and this will import without errors. Is it when you try to use the service that you get the error or when importing the app service?