[CentOS] yum update -> [Errno 4] Socket Error: timed out

Trying to update a second CentOS box, I'm getting this error repeatedly:

[Errno 4] Socket Error: timed out

I'm getting this on every mirror and have gone through the list of mirrors more than a dozen times.

Oddly, the RPMs I'm trying to upgrade I upgraded just yesterday without a problem on another machine on the same LAN with no problems whatsoever. I can ping mirrors fine.

There were a spate of these errors back in 2006. The fix for many was to add this line to yum.conf:

timeout=300

So I did that on the machine where yum is having the problem, but the same errors are returned.

Anyone else seeing this? Anyone know what the problem is?