@James Redway: you need at least to check the last error when copying. When you get -5000 as error then you can’t write to the folder.
Add another user to your computer without admin rights for testing.
@Kevin Gale: shudder. I’m now up to 6 apps: main app, installer, helper app. Helper app for bug in Evernote. Another helper app for the server version. What did I forget?