imlib doesn't seem to be properly checking whether the MIT SHM extension supports shared pixmaps. In the case of an X driver using EXA, shared pixmaps aren't available, which causes imlib to fail to load images properly in some cases. More details and a patch available at http://bugs.debian.org/448360.
Patch applied in imlib 1:1.9.15-5.fc9. Updates for F7 and F8 to follow.
imlib-1.9.15-5.fc8 has been pushed to the Fedora 8 testing repository. If problems still persist, please make note of it in this bug report. If you want to test the update, you can install it with su -c 'yum --enablerepo=updates-testing update imlib'
imlib-1.9.15-6.fcX has been pushed for Rawhide, Fedora 6, 7, and 8, and includes the patch to address this issue.