I am having this issue as well and cannot see the solution.
The solution was explained in the thread I linked:
http://www.fsdreamteam.com/forum/index.php/topic,14211.msg107100.html#msg107100 What exactly am I supposed to do to correct this problem?
Quoting from that thread:
The solution to this problem, which is a XML file corruption caused by another defective 3rd party product (it was confirmed an OUTDATED version of Active Sky caused this problem, but there might be others around doing the same), is to open the XML file using a text editor that lets you change the file encoding, change to ANSI, and save it back.
An example of an editor that can do this, is the free Notepad++
If a file needs to be changed, where is that file?
Sorry, I realized that thread was probably in reply to something else, so it didn't included all information required. P3D has two locations for the XML files:
%APPDATA%\Lockheed Martin\Prepar3D V3
%PROGRAMDATA%\Lockheed Martin\Prepar3D V3
There are two XML files on each folder, EXE.XML and DLL.XML, so you have a total of 4 XML files to check. Which means, doing what has been explained on that thread, which I quoted again here:
to open the XML file using a text editor that lets you change the file encoding, change to ANSI, and save it back.
