An image which contains a value for the EXIF rotation field is automatically displayed (rotated) correctly in Photoshop. This behavior seems to have a side-effect when using AD. When you open such an image from AD, Photoshop automatically checks out the file while no real modifications are made. The file stays checked out if you just close it.
Mac OSX 10.6.8
Adobe Drive 3.2
How to reproduce
Check-in an image which contains an EXIF rotation (for example from a camera)