This behavior started this morning all of a sudden. After checking every step on
http://wordfaqs.mvps.org/InvisibleGraphics.htm
I still can't see pasted images.
This is what you can see after clicking the box where the image should show

I cannot see them in print preview either, not even after saving the document as a pdf.
In previous documents I can indeed see images pasted in the same fashion.
The only way I can paste images now is copying just one picture at once and pasting it as a bit map. Copying one at a time and pasting them via Ctrl+V, pastes them in a small size all in a row.
Here's a document showing such a behavior