Microsoft Project Enterprise 2007. Cannot create application-object

Dear readers,

I have in my code:

       MsProject.Application inst = new MsProject.Application();

I get a error-message as: 

"TPG ProjectLink 2010.    ProjectServer: Online Profile required   ProjectLink can't operate with an offline profile. An online profile connected to the project server is required".

I am lost. Can somebody give me a hint?

Update: I found out now, that this code works, if I have MsProject opened manually before

Thank you in advance