CSS for Custom Components not being found in NetWeaver

I'm using the design studio SDK to develop a set of custom components in Design Studio 1.4.  They contain both javascript and css files.  The components are working fine when running in local mode but when I run them on NetWeaver (v7.3) none of the associated CSS files are being found. All URL calls to pull a css file are returning 500 errors.  The logs are giving “Resource not found:” errors. None of my components are using images so I don’t know if that works but I do know that all the javascript files are coming across ok.

Does any one have any ideas I might try?

Thanks

David