Updating via yum/up2date

[Jon 780]

I'm having a hell of a time updating my fc4test3 installation.

Yum, after downloading 700 or so MB worth of packages, tells me it
couldn't find any mirrors for about 10 packages, and exits.  So I try
again, and it attempts to download every package again.  Why doesn't
it just check to see what was already downloaded and skip what's
already there?  That seems patently ridiculious to me.

up2date, that just gives me a 404 on the header.info file.

So what am I doing wrong, why is something that should be so
incredibly simple, such an incredible pain in my ass?

.jon