Shared Data Source Help

Hello

I have a requirement, to add a Shared Data Source (SharePoint List) that instead of a URL, has [@URL] in it - which is a parameter generated from some SQL queries in lots of occasions in separate sub reports.

This concept works fine as a local Data Source in a report, however, when trying to deploy the Shared Data Source I have made, this error creeps up;

Object reference not set to an instance of an object.

Any ideas why I cannot deploy it?

If I add the Shared Data Source in the actual Native SSRS site, that works ok too. Its just using visual studio, does not work.............

I am pretty new, so easy to understand help would be greatly received!!!!!!!!!!!!