A user is able to ping an FTP server across a WAN but is unable to download files from the server What should be checked to resolve this problem?

What exactly do you mean when you say "unable to download" - are they getting an error message. Is the download just not starting. Is the download being interuppted..??

It could be something to do with permissions. It could be a firewall not configured properly- allowing icmp traffic but blocking ftp traffic - it could be alot of different things. Need more details.