probably, you don't do anything wrong, it should work. Just to isolate the error: try to drag the link attribute into the model pane, and double click onto it (or whatever you do instead of double click on your Apple).
And what kind of link is it? It is another ADF file, right?
Ah, besides: just a remark: Express is released for Windows only. Unix and Apple are not supported (maybe this is also the reason for that here: "www.ariscommunity.com/users/ganeshjanakiraman/2009-08-08-mouse-over-preview-start-page"). Nevertheless I hope we can find out what the bug is.