<APPLICATION_PATH> is initialized by GetExecutingAssembly, which sets it to MediaPortal.Common.dll in some cases.

https://github.com/MediaPortal/MediaPortal-2/blob/c621457a6416d2147560dae346c8e0dfd058c267/MediaPortal/Source/Core/MediaPortal.Common/Services/PathManager/PathManager.cs#L66

Not sure why it is working for the existing components (client, server, servicemonitor), but it is not working for MP2-ClientLauncher.

h4. Additional Information
For more infos see: http://stackoverflow.com/questions/1642827/finding-my-main-executables-path-using-assembly-vs-appdomain