Thanks BooksonBoard, I have now managed to attach my 505 to my imac. Now the Windows beast may meet it's end.
Footnote for those having problems, as I did, transferring books from the mac ADE into the reader. Click on Documents on the right hand side of the 'Dock', now click on the Digital Editions Folder. Drag and drop book titles from the Finder folder onto the Ebook icon on your desktop.