Ive tried Archlinux about 3-4 months ago.Nice distro..but I always seem to come back to debian..Might try it again in future.But anyway..did you follow the Beginners Guide to installing Arch??Can you.
ping -c 3 www.google.com
If you can connect..maybe it is a issue with the server you choose..try selecting another server in mirrorlist.You did choose another server??
archlinux.org is throttled to 50KB/s
Also maybe you didnt setup things right..Maybe check out your
/etc/hosts.deny and /etc/hosts.allow