A broken Arrow like below, means that Aperture has lost the connection to the original image files.
If your images are referenced, and if you know, where the originals are stored, you can point Aperture to the correct location.
Use the "File > Locate Refererenced Files" command.
This will show a panel, where the upper part is showing the images with missing originals. Select one of them, and you can see the path to the missing original below the Thumbnail.
In the lower part of the panel is a file chooser, where you can point Aperture to the missing file, if you know the location. Press the "Reconnect all" button, if it becomes active.