Internal error in apt-get

[Francesco Potorti` <F.Potorti@cnuce.cnr.it>]

I got this:

# pwd
/var/cache/apt/archives
# ls -l tetex-*
-rw-r--r--   1 root     root      3497718 Oct 13 13:57 tetex-base_0.9.981008-1.deb
-rw-r--r--   1 root     root      3271592 Oct 13 13:57 tetex-bin_0.9.981008-1.deb
-rw-r--r--   1 root     root        61762 Oct 13 13:57 tetex-dev_0.9.981008-1.deb
-rw-r--r--   1 root     root      8942710 Oct 13 13:57 tetex-extra_0.9.981008-1.deb
-rw-r--r--   1 root     root       633420 Oct 13 13:57 tetex-nonfree_0.9.981008-1.deb
# apt-get -m upgrade
Updating package status cache...done
Checking system integrity...ok
The following packages have been kept back
  tetex-nonfree tetex-bin
5 packages upgraded, 0 newly installed, 0 to remove and 2 not upgraded.
32 packages not fully installed or removed.
Need to get 309k/13.1M of archives. After unpacking 5827k will be used.
Do you want to continue? [Y/n]
Get ftp://ftp2.mathematik.tu-darmstadt.de slink/main base-files [20.7k]
Error ftp://ftp2.mathematik.tu-darmstadt.de slink/main base-files
 550 /pub/linux/distributions/debian/dists/unstable/main/binary-i386/base/base-files_2.0.2.deb: not
a plain file.
Get ftp://ftp2.mathematik.tu-darmstadt.de slink/main plplot-doc [289k]
Error ftp://ftp2.mathematik.tu-darmstadt.de slink/main plplot-doc
 550 /pub/linux/distributions/debian/dists/unstable/main/binary-i386/math/plplot-doc_4.99j-4.deb: not a plain file.
W: Couldn't locate an archive source for package tetex-bin
E: Internal Error, No file name for tetex-bin