[BitBucket user: Stefan Schiele]
[BitBucket date: 2017-11-09.09:39:36]

If you give permission to let the Orthanc service interact with the desktop you can observe this message.
The log file points to the problem: If you create a backup copy of the configuration file "orthanc.json" in the same directory the Orthanc service refuses to start.
Anyway, thanks for your advise !

Log:
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W1108 09:47:32.283203 main.cpp:1269] Orthanc version: 1.3.0
W1108 09:47:32.283203 OrthancInitialization.cpp:174] Scanning folder "Configuration" for configuration iles
W1108 09:47:32.283203 OrthancInitialization.cpp:126] Reading the configuration from: "Configuration\dicomweb.json"
W1108 09:47:32.283203 OrthancInitialization.cpp:126] Reading the configuration from: "Configuration\orig__orthanc.json"
W1108 09:47:32.283203 OrthancInitialization.cpp:126] Reading the configuration from: "Configuration\orthanc.json"
E1108 09:47:32.283203 OrthancInitialization.cpp:157] The configuration section "AllowFindSopClassesInStudy" is defined in 2 different configuration files
E1108 09:47:32.283203 main.cpp:1295] Uncaught exception, stopping now: [Bad file format] (code 15)
W1108 09:47:32.283203 main.cpp:1328] Orthanc has stopped
---