Cannot create a connection to data source 'myDataset'

I almost pulled the hair out of my head trying to resolve this stupid error when working with SQL
Reporting Expresses Data source connection limitations;
Cannot create a connection to data source 'myDataset'

The solution is quite simple yet mystifying, the two connection strings below should be pointing to the same database

Does not work in Reporting Services Express: Server='MyDataBase\SQLEXPRESS';Database=Catalog;
Works in Reporting Services Express: Server=MyDataBase\SQLEXPRESS; Database=Catalog;

In case you miss the difference, you are apparently not allowed inverted commas around your attribute names.

Hope someone finds this helpfull