I think the problem is some device that cannot handle the 'Range' HTTP tag. See below for a proof:

ns1:~# telnet linux3.cc.ntu.edu.tw 80
Trying 140.112.8.139...
Connected to linux3.cc.ntu.edu.tw.
Escape character is '^]'.
GET /debian/dists/etch/Release.gpg HTTP/1.1
Host: linux3.cc.ntu.edu.tw
Range: bytes=188-
If-Range: Wed, 09 May 2007 08:17:15 GMT
User-Agent: Debian APT-HTTP/1.3

Connection closed by foreign host.

Now, let's try without the 'Range' HTTP tag:

ns1:~# telnet linux3.cc.ntu.edu.tw 80
Trying 140.112.8.139...
Connected to linux3.cc.ntu.edu.tw.
Escape character is '^]'.
GET /debian/dists/etch/Release.gpg HTTP/1.1
Host: linux3.cc.ntu.edu.tw
If-Range: Wed, 09 May 2007 08:17:15 GMT
User-Agent: Debian APT-HTTP/1.3

HTTP/1.1 200 OK
Date: Wed, 06 Jun 2007 02:57:44 GMT
Server: Apache/2.2.3 (Debian) mod_ssl/2.2.3 OpenSSL/0.9.8c
Last-Modified: Sun, 08 Apr 2007 10:49:13 GMT
ETag: "b128-17a-42d97abd4bc40"
Accept-Ranges: bytes
Content-Length: 378
Content-Type: text/plain; charset=UTF-8

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.1 (GNU/Linux)

iD8DBQBGGMb4pw2vU2Bw06ERAmPbAJ4wTvLZlocu/sTJBGBxaS0TXhT6hgCbBnQl
Rlof3xGJXxYnsUoHishfZMY=
=QSdS
-----END PGP SIGNATURE-----
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (GNU/Linux)

iD8DBQBGGLggtdDIBK2xEncRAl8+AJwNeefC/JOB7dz6cbKjym2MjywKQACfeuCJ
4MbfYYrUSg4wi7D4fs/Tv4g=
=flEJ
-----END PGP SIGNATURE-----
Connection closed by foreign host.