I had already tried it and it doesn't work "the selected element has been modified in iphoto and cannot be updated" (L’élément sélectionné a été modifié en externe dans iPhoto et ne peut être mis à jour.)
here are screencaps to show you what it looks like.
So everything is normal in iphoto, then I double click on an image in aperture and this happens, then the thumbnails are destroyed, and then in iphoto it is also destroyed.
I have the same problem.
In somme cases (dans certains cas... Pas sûr de la bonne traduction...) , I re-imported the originals but it's not useful :-/
As some of the albums who encouters this problem are shared on Flickr Via iPhoto-Aperture uploader, I've, with some apprehension, tried to correct the problem via iPhoto, but as the refreshing of the thumbmail didn't happens after some minutes, I disconnected fast, being affraid of the possibly to corruption of my Aperture to Flickr publication of more than 20K photos, thinging at the numbers of hours of synchronisation...