sibling clients get access denied for ftp objects

Hi all,

I recently encountered the following problem: Sometimes, when a client
from one of our siblings tries to fetch an (ftp) object, he gets the
following error message (from our cache, that is proxy.belnet.be,
running squid-1.1.15):

Error

Access Denied

Sorry, you are not currently allowed to request:

ftp://ftp.autodesk.com/pub/autocad/patches/r13c1/r13c1u1.exe

from this cache. Please check with the cache administrator if
you believe this is incorrect.

proxy@belnet.be

Generated by squid/1.1.15@proxy.belnet.be

When I try to access the same object it gets downloaded without problems.

In the access.log I see a UDP_HIT (from the sibling) immediately followed
by a TCP_DENIED (from the same sibling). When I try to access that object
immediately after that, I get a TCP_HIT and the whole thing downloads.
It seems to happen only with FTP transfers and is not limited to one
specific sibling. Anyone knows what is going on?

Thanks,

--
Jan Torreele				E-mail: Jan.Torreele@belnet.be
BELNET Service Support Team		Tel.:	 +32 (0) 2 / 238 34 70