Access problems with squid FTP

Can anyone tell-me why the line:

bin/client -h proxy.sibling.pt ftp://ftp.site.pt/pub/pt/local/

receives a denied from most of my siblings and:

bin/client -h proxy.sibling.pt ftp://ftp.site.pt/pub/pt/local

works perfectly ?

I'm using squid 1.1.10 ( 1.1.9 produces the same result )

Thanks in advance.

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        Pedro Ribeiro
        Online: http://www.cc.isel.pt/Pessoais/PedroRibeiro
        e-Mail: Personal: pribeiro@cc.isel.pt
                Admin: admin@isel.pt
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Received on Tue Apr 29 1997 - 12:20:26 MDT