Why is iWork Keynote is suddenly linking images instead of embedding them? I've been using iWork for a while and have created some pretty elaborate designs in Keynote and Pages, but I haven't come across a problem like this before or even an option to link/embed images.

In Keynote, all my images are now linked to an external source on my hard disk, rather than embedded in the file itself. When I attempt to copy media in any manner (alt-drag or cmd+c/v or duplicate a page), a grey "placeholder" box is produced with a question mark in the middle and a diagonal line across it (see top right corner of the image).

It only works when the source image is in the same place on my hard disk.

When I insert an image or other media file (insert -> choose) into Keynote, there doesn't seem to be an option to link or embed like there is in other applications such as Adobe Illustrator or InDesign.

Why is Keynote all of a sudden treating images in this fashion? How can I fix this to re-enable embedding of images?
go to Keynote > Preferences > under general Preferences make sure under Saving: "include Preview in document by default" and "copy auto and Movies into Document" is checked.