Thanks for your reply.
It seems to me one reason could be the upfintf package (which contains the ApplicationService variable) is not consistently seem by the application and the plugin.
One reason may be differing search paths (I haven't verified this yet).
Since the demo projects work there should be some viosible differences between project options.
I'll go through the project settings and get back with the sample project if the problem still persists.
regards,
Jouni