proxy for apt-get?

[Andy Spiegl <debian-user.andy@spiegl.de>]

I am trying to tune apt-get to use my proxy (squid) when downloading files
via ftp, but it doesn't connect anymore when I write this file:
 /etc/apt/apt.conf.d/20proxy
with this content:
--------------------------
Acquire
{
  ftp
  {
    Proxy "ftp://proxy:3128/";;
  };
};
--------------------------

Or:
    Proxy "http://proxy:3128/";;

All I get is this:

 hamster:~#apt-get install wine
 Reading Package Lists... Done
 Building Dependency Tree... Done
 The following extra packages will be installed:
   libcupsys2 libwine wine-utils 
 4 packages upgraded, 0 newly installed, 0 to remove and 864  not upgraded.
 Need to get 5405kB of archives. After unpacking 423kB will be used.
 Do you want to continue? [Y/n] 
 0% [Logging in]
Err ftp://ftp.de.debian.org woody/main libcupsys2 1.1.12-4
  Server closed the connection
 0% [Logging in]
Err ftp://ftp.de.debian.org woody/main wine 0.0.20011226-1
  Server closed the connection
 0% [Logging in]
...

But the cache _does_ work.  Proof:
 hamster:~>telnet proxy 3128
 Trying 192.168.96.3...
 Connected to proxy.int.radiomaranon.org.pe.
 Escape character is '^]'.

Any idea what I'm doing wrong?
Thanks,
 Andy.

-- 
 Dr. Andy Spiegl, Radio Marañón, Jaén, Perú
 E-Mail: Andy@spiegl.de, Andy@radiomaranon.org.pe
 URL: http://spiegl.de, http://radiomaranon.org.pe
 PGP/GPG: see headers
                              o      _     _         _
  ------- __o       __o      /\_   _ \\o  (_)\__/o  (_)          -o)
  ----- _`\<,_    _`\<,_    _>(_) (_)/<_    \_| \   _|/' \/       /\\
  ---- (_)/ (_)  (_)/ (_)  (_)        (_)   (_)    (_)'  _\o_    _\_v
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 Children seldom misquote you.  Usually they repeat word for
 word what you shouldn't have said.