Have you try IE locally in the machine ?
this should relate to the famous passive mode issue.
lazy to type now

http://groups.google.com/groups?hl=en&lr=&c2coff=1&q=IIS+FTP+Passive+Mode+Bernard+Cheah
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Regards,
Bernard Cheah
http://www.tryiis.com/
http://support.microsoft.com/
http://www.msmvps.com/bernard/