Database Diagram + Reporting Services/Report Builder

If I make a new database, why is it that VS 2005 server explorer can see it, access the tables and stored procs, etc ... but when using Reporting Services/Report Builder after I make the data source and generate the model NOTHING APPEARS in Report Builder (message about "there is no content in this data source")..

now this has been driving me nuts for a few days and the solution was to click on "DataBase Diagram" in Sql Managment studio for that DB and say "Yes" to the dialog that appears

My question is why is that the case

Carl