Unavailable packages question

[Neil Booth <neil@daikokuya.demon.co.uk>]

This is the output of a couple of dpkg commands on my system:-

monkey:/home/neil# dpkg -l "mutt*"
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Installed/Config-files/Unpacked/Failed-config/Half-installed
|/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err: uppercase=bad)
||/ Name                     Version                  Description
+++-========================-========================-================================================================
ii  mutt                     1.3.15-2                 Text-based mailreader supporting MIME, GPG, PGP and threading.
un  mutt-i                   <none>                   (no description available)
rc  mutt-ja                  0.95.4i.jp2-2.1          Text-based mailreader for Japanese.
un  muttzilla                <none>                   (no description available)

monkey:/home/neil# dpkg -p mutt-i 
Package `mutt-i' is not available.

Use dpkg --info (= dpkg-deb --info) to examine archive files,
and dpkg --contents (= dpkg-deb --contents) to list their contents.


So, why is "mutt-i" still listed if it is not available?  How can I
flush these "unavailable" packages so they don't clutter up the
packaging system?  dpkg --forget-old-unavail appears to be what I
want, but it does nothing from what I can surmise.

Thanks,

Neil.