The problems:
The file is saved as UTF-8 not UTF-16.
The header is wrong in the XML file:
xml code:
<?xml version="1.0" encoding="UTF-16"?>
<Interfaces xmlns="urn:msgplus:interface" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:msgplus:interface PlusInterface.xsd">