The spice-client-gtk-3.0.pc file has a Requires on a nonexisting spice-client-glib-3.0. It needs to require spice-client-glib-2.0 instead.
Package spice-gtk-0.5-6.fc15: * should fix your issue, * was pushed to the Fedora 15 updates-testing repository, * should be available at your local mirror within two days. Update it with: # su -c 'yum update --enablerepo=updates-testing spice-gtk-0.5-6.fc15' as soon as you are able to, then reboot. Please go to the following url: https://admin.fedoraproject.org/updates/spice-gtk-0.5-6.fc15 then log in and leave karma (feedback).
spice-gtk-0.5-6.fc15 has been pushed to the Fedora 15 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 spice-gtk'. You can provide feedback for this update here: https://admin.fedoraproject.org/updates/spice-gtk-0.5-6.fc15
spice-gtk-0.5-6.fc15 has been pushed to the Fedora 15 stable repository. If problems still persist, please make note of it in this bug report.