[debian-users:24730] dpkg upgrade にてエラー

[Akimichi Tatsukawa <akimichi@xxxxxxxxxx>]

こんにちは、立川と申します。
ThinkPadにpotatoを新規インストールして dpkg -f upgrade を実行したところ、
以下のようなエラーメッセージが出てストップしてしまいました。

Reading Package Lists...
Building Dependency Tree...
The following packages have been kept back
  navigator pcmcia-modules-2.2.17 
37 packages upgraded, 0 newly installed, 0 to remove and 2 not upgraded.
Need to get 0B/49.2MB of archives. After unpacking 7785kB will be freed.
Do you want to continue? [Y/n] 
2% [Scanning packages]
5% [Scanning packages]
8% [Scanning packages]
10% [Scanning packages]
13% [Scanning packages]
16% [Scanning packages]
18% [Scanning packages]
21% [Scanning packages]
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29% [Scanning packages]
32% [Scanning packages]
35% [Scanning packages]
37% [Scanning packages]Template does not contain a Template: line at /usr/lib/perl5/Debian/DebConf/Template.pm line 109, <TEMPLATES> chunk 42.
E: Sub-process /usr/sbin/dpkg-preconfigure --apt returned an error code (29)
E: Failure running script /usr/sbin/dpkg-preconfigure --apt

問題の /usr/lib/perl5/Debian/DebConf/Template.pm line 109 付近は次のようになっていました。

sub parse {
	my $this=shift;
	my $text=shift;

	my ($field, $value, $extended)=('', '', '');
	foreach (split "\n", $text) {
		chomp;
		if (/^([-_.A-Za-z0-9]*): (.*)/) {
			# Beginning of new item.
			$this->_savefield($field, $value, $extended);
			$field=lc $1;
			$value=$2;
			$extended='';
		}
		elsif (/^\s+\.$/) {
			# Continuation of item that contains only a blank line.
			$extended.="\n\n";
		}
		elsif (/^\s+(.*)/) {
			# Continuation of item.
			$extended.=$1." ";
		}
		else {
			die "Template parse error near \"$_\"";
		}
	}

	$this->_savefield($field, $value, $extended);

	# Sanity checks.
	die "Template does not contain a Template: line" <== ここが問題の109行です
		unless $this->{template};
}

関係ないかも知れませんが source.list は次の通りです。

deb ftp://pano.localdomain/debian potato main contrib
deb ftp://ring.so-net.ne.jp/pub/linux/debian/debian/ potato main non-free
deb ftp://ring.so-net.ne.jp/pub/linux/debian/debian-jp/ potato-jp main contrib non-free
deb ftp://ftp2.linux.or.jp/pub/Linux/debian-jp potato-jp main contrib non-free
deb ftp://ring.so-net.ne.jp/pub/linux/debian/debian-non-US/ dists/potato/non-US/main/binary-i386/
deb ftp://ring.so-net.ne.jp/pub/linux/debian/debian-non-US/ dists/potato/non-US/contrib/binary-i386/
deb ftp://ring.so-net.ne.jp/pub/linux/debian/debian-non-US/ dists/potato/non-US/non-free/binary-i386/
deb ftp://ring.so-net.ne.jp/pub/linux/debian/debian/ dists/potato-proposed-updates/
deb ftp://ring.so-net.ne.jp/pub/linux/debian/debian-jp/ dists/potato-jp-proposed-updates/

私には何がおかしいのか皆目見当もつかず、途方に暮れております。
ご存じの方がいらっしゃいましたら、教えていただければ幸いです。