This is a bit of a guess, but you might try disabling the ARD widget (don't just close it, use the Manage Widgets screen to completely disable it) and re-enabling it and see if it will then pick up your lists.
Upon launching Remote Desktop I was always prompted for my password to use the software which I never stored in my keychain. As soon as I said store my password in the keychain and reloaded the widget I was asked to allow the widget access to my keychain and then all my lists showed ok.