Schema can't be load

Hi

I have an application which contains two receive locations (HTTP and FILE). Both are using the same "XMLReceive" Pipeline. A receiveport in an orchestration with a direct binding is "listening" to xml files which are belong to a schema.

But then I send an XML-File over the HTTP adapter I am getting the error:

The document specification <CL.External.Controlware.SCHEMAS.PurchaseOrder> from assembly <CL.External.Controlware.SCHEMAS, Version=1.0.0.0, Culture=neutral, PublicKeyToken=413e9d4e7ea53c6e> failed to load. Verify the schema for this document specification is deployed and is in the Global Assembly Cache. 

But the schema has been deployed properly into the GAC (gacutil /l CL.External.Controlware.SCHEMAS) as you can see in the screenshot below: (HostINstances have been restarted as well)

BUT when I place the same xml file into the file receive location it will be processed without any problem.

Where is the error?

Thank you!