Error System.IO.FileNotFoundException

It runs fine when im executing from my .Net Dev Environment. But when I execute the exe file on it's own I get the following error message:

An unhandled exception of Type 'System.IO.FileNotFoundException' occurred in sapsolution.exe

Additional information: File- or assemblyname Interop.SAPbouiCOM or one of its dependencies wasnt found.

Any clue on what might be wrong? Did I fail to add something. Somewhere?

The best regards

Allan, Denmark