This dialog shows up in the latest version of Panther (10.3.2). One of the new features in Panther is that you can keep a local version of your iDisk on your desktop at all times, and then sync it automatically or manually. This is great to not have to mount the iDisk every time I want to access it.
In the initial release of 10.3 I used to get dialog boxes such as this one, but they were not as nice. Mirror Agent (the application that runs in the background to help with this iDisk feature, has cancelled my logout about 3 times. But before I was never given the choice to force quit the app. Now in 10.3.2 I can. I like that.
