I have an analysis services database which contains datasources, data source views, dimensions and cubes. I want to edit the Project Properties for it by right-clicking the highest level, then clicking properties, but I don't get anything: it doesn't show the properties. If I create a new empty project I can get the properties page without difficulty.
Is it possible that this is blocked for security reasons? Or is it something else?
It sounds like you have used the BIDS menu command File / Open / Analysis Services Database. In that case you are directly editing the schema. Clicking Save will "deploy" your changes.