Ah, I found some info on the issue:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=130183
Seems like the bug is fixed in gtk-2.4.9. I wonder why 2.4.7 was released as an official FC2 update, without the patch which fixes the thumbnail problem.
Security over eye-candy, I guess.
If you want your cool nautilus thumbnails back the way they were before,
(and don't mind a few security buffer overflow issues, but really, you should) download:
http://download.fedora.redhat.com/pub/fedora/linux/core/2/i386/os/Fedora/RPMS/gtk2-2.4.0-1.i386.rpm
http://download.fedora.redhat.com/pub/fedora/linux/core/2/i386/os/Fedora/RPMS/gtk2-devel-2.4.0-1.i386.rpm
http://download.fedora.redhat.com/pub/fedora/linux/core/2/i386/os/Fedora/RPMS/gdk-pixbuf-0.22.0-5.0.1.i386.rpm
..and do as root: rpm --force -Fvh gdk-pixbuf-0.22.0-5.0.1.i386.rpm \ gtk2-2.4.0-1.i386.rpm gtk2-devel-2.4.0-1.i386.rpm
..then wait for a new GTK2 update to come along.
Never accept a carefully crafted image file from a stranger :o).
Cheers, Øyvind -- < Øyvind Stegard <oyvinst (at) ifi uio no> < University of Oslo, Dept. of informatics < http://www.stegard.net/ < "If at first you do succeed, try not to look astonished."