That was a deliberate change. Before this change selecting a group containing a few hundred items would look up GarageSale, (especially on slower Macs) because all listings had to be loaded from disk to computer the correct display values in the inspector.
If you want the old behavior, you have to click on a listing in the overview mode to move the focus and press command-A afterwards.
Just saw this happening, too. Very odd indeed. We’ll look into this.
For the record:
*Preview mode => shows an editbale mock-up of the eBay listing for a single listing
*Overview mode => shows several items in either as thumbnails or as table view