This has become a common problem lately in the past several months and
is out of Microsoft's control.
Your ISP's DNS servers, which resolve server names to IP addresses so
that your machine can connect, have given your Mac some bad information.
First, try clearing your computer's DNS cache. It's quick and causes no
harm:
1. Open the Terminal application found in /Applications/Utilities.
2. Enter this command followed by a return:
dscacheutil -flushcache (for Leopard)
lookupd -flushcache (for Tiger)
3. Try your download again. Your machine should have to query your DNS
servers again for an address.
If the above doesn't work then your ISP's DNS servers are still causing
you a problem. Look into using <
http://www.opendns.org/> to substitute
your ISP's DNS server addresses with this service's DNS servers. It's
also very simple and will very probably allow you to download your
updates. You may need to run the above Terminal command again after
changing your DNS servers.
You might also consider just using these new DNS server addresses
permanently. See if your speed accessing websites improves and note
whether or not you have fewer or more problems connecting to sites.
For more information have a look at this blog post:
"Unable to download updates"
<
http://blog.entourage.mvps.org/2008/07/unable_to_download_updates.html>
