tumbler currently uses the deprecated GDK pixbuf API of poppler-glib (poppler_page_get_thumbnail_pixbuf() and poppler_page_render_to_pixbuf(), in particular), which has been dropped starting from poppler 0.17.0 (unstable version for the next stable 0.18). Please migrate the rendering code to cairo (which is available in poppler-glib since at least 0.8 or so). For more details, see the blog of the poppler-glib developer: http://carlosgc.linups.org/gnome/gdk-api-removed-poppler.html
Fixed in master: commit df3e439da778d60b4c86ec24c0c6a98e7a5f831d Author: Jannis Pohlmann <jannis@xfce.org> Date: Mon May 23 15:38:33 2011 +0200 Avoid GdkPixbuf functions deprecated in poppler >= 0.17 (bug #7649).