libproxy no mirror

Hi. I'm doing an update in Fedora 17 but I encounter this errors:

libproxy-0.4.11-1.fc17.x86_64: [Errno 256] No more mirrors to try.
libproxy-mozjs-0.4.11-1.fc17.x86_64: [Errno 256] No more mirrors to try.

Any help is appreciated. :)