Strange effects happen. If the <propertyList>-tag has an include and this include points to a file outside of the current plane project, for example, my JPack, the plane doesn't show up in the launcher. It works with the FGRun delivered with 3.0, I had no chnace to chekc on 3.2 and the error doesn't occur with the 3.5 (thanks IAHM-COL for checking this out). So it's once more the 3.4 packet ... well, no surprise there.
Well, we are already waiting for the "official" 3.6 coming with Qt5 and all the bells and whistles, so the problem is probably kind of outdated and worth no error report anymore, but if someone has a workaround for the poor people unable to start FG under Windows from a command prompt, I guess, it would be appreciated.