Current stable version is 0.6.3: http://archive.xfce.org/src/apps/ristretto/0.6 Current version in Fedora is 0.6.0. Please update.
ristretto-0.6.3-1.fc18 has been submitted as an update for Fedora 18. https://admin.fedoraproject.org/updates/ristretto-0.6.3-1.fc18
ristretto-0.6.3-1.fc18 has been pushed to the Fedora 18 stable repository. If problems still persist, please make note of it in this bug report.