Stuck in a loop with yum

[pianoplayer]

I tried to run a simple yum update, no different from many others that I have run successfully. This time, I got an endless loop of the following

Trying other mirror.
primary.xml.gz 100% |=========================| 337 kB 00:04
http://mirror.optus.net/fedora/core/...rimary.xml.gz: [Errno -1] Metadata file does not match checksum
Trying other mirror. . . .

The same sequence then repeated, mirror after mirror after mirror, ending with the message

Error: failure: repodata/primary.xml.gz from updates: [Errno 256] No more mirrors to try.

What is going on? Have the sites around the world changed something in the past week? Is a file of mine corrupted? Or is it something else?

[Roxoff]

Nahh, it's just a glitch in the matrix - give it a few hours and try again.

[pianoplayer]

As Roxoff suggested, I tried the same update a few hours later, and everything worked as expected.

What is "the matrix"? Just what does yum do behind the scenes?

[Roxoff]

The matrix? It's an energy field; it surrounds us, it penetrates us, it binds the universe together...

Oh, hang on a moment, wrong film.

No, it's a massive computer program like a big virtual reality game in which all human life is plugged into to disguise the fact that we're spending our lives living in a little pod never needing a haircut or needing to shave, and providing energy to a big supercomputer that we cant defeat.