eset seculity　のアプリケーションパケットフィルタを有効にして
それが邪魔しているとかじゃないですか？

知らなかったこととはいえ、失礼いたしました

申し訳ありません

http://forum.mozilla.gr.jp/?mode=all&namber=41043&type=0&space=0&
もじら組で質問されているれんさんですね？
[url=http://ja.wikipedia.org/wiki/%E3%83%9E%E3%83%AB%E3%83%81%E3%83%9D%E3%82%B9%E3%83%88]マルチポスト[/url]という言葉をご存知でしょうか？

http://www.mozilla-japan.org/addons/firefox/
及び
https://addons.mozilla.org/ja/firefox/

にてアドオンをダウンロードしようとするのですが。

有線LANで接続→ダウンロードエラー228
この状態からLANケーブルを抜き無線LANで接続しなおすと
正常にダウンロード完了

どちらも特にインターネットへの接続に問題は無く、接続に使用しているフレッツ光
の光電話対応ルーターRV－２３０NEで無線カードを外し有線のみにしても×

なお有線LANでもAdd-onsのサンドボックス及びhttp://norahmodel.exblog.jp/
等のサイトではまったく問題なくダウンロードできます

環境としてはOS　Windows　VISTA　HomePremium
ネット接続は上記RV－２３０NEをインターネット接続設定したのみの状態で確認（初期化）
PCは自作及びHPのノートPC両方で出ます
念のため、VISTAクリーンインストール→FireFoxをダウンロードしなおしたまっさらな状態で確認
してみましたが同じ状況です
（プラウザのキャッシュは毎回クリアし、ダウンロード出来たアドオンもアンインストールして確認）

また念のため、フレッツ光のサポートに確認してみましたが、原因となるものが考えづらいとの事
あとmozilla-japanのサポートみてみましたが、エンドユーザーの問題には対応していないとの
ことなので、mozilla-japan側サーバーの問題かどうかは確認出来てません
一度送ってみたのですが、コミュニティにて確認して下さいとのことでしたし

アドオンでHTTPログとれるものがあったので
有線LAN時　ダウンロードエラー

https://addons.mozilla.org/ja/firefox/downloads/file/13583/minkaku-1.3-fx.xpi

GET /ja/firefox/downloads/file/13583/minkaku-1.3-fx.xpi HTTP/1.1
Host: addons.mozilla.org
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; ja; rv:1.8.1.12) Gecko/20080201 Firefox/2.0.0.12
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language: ja,en-us;q=0.7,en;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: Shift_JIS,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Cookie: __utmz=164683759.1204289207.7.6.utmccn=(referral)|utmcsr=mozilla-japan.org|utmcct=/addons/firefox/|utmcmd=referral; __utma=164683759.1355901390.1204227280.1204283674.1204289207.7; __utmb=164683759; __utmc=164683759

HTTP/1.x 302 Found
Age: 173
Date: Fri, 29 Feb 2008 12:43:32 GMT
Expires: Fri, 29 Feb 2008 13:43:41 GMT
Cache-Control: max-age=3600 ,public
Connection: Keep-Alive
Via: NS-CACHE-6.0: 4
Server: Apache/2.0.52 (Red Hat)
X-Powered-By: PHP/4.3.9
X-AMO-ServedBy: mrapp03
Last-Modified: Fri, 29 Feb 2008 12:43:41 GMT
Location: http://releases.mozilla.org/pub/mozilla.org/addons/4562/minkaku-1.3-fx.xpi
Content-Length: 0
Content-Type: text/html; charset=UTF-8
----------------------------------------------------------
http://sb.google.com/safebrowsing/update?client=navclient-auto-ffox&appver=2.0.0.12&version=goog-white-domain:1:29,goog-white-url:1:371,goog-black-url:1:18907,goog-black-enchash:1:45634

GET /safebrowsing/update?client=navclient-auto-ffox&appver=2.0.0.12&version=goog-white-domain:1:29,goog-white-url:1:371,goog-black-url:1:18907,goog-black-enchash:1:45634 HTTP/1.1
Host: sb.google.com
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; ja; rv:1.8.1.12) Gecko/20080201 Firefox/2.0.0.12
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language: ja,en-us;q=0.7,en;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: Shift_JIS,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Cookie: PREF=ID=4c158eb9579238bf:TM=1204282835:LM=1204282835:S=mukcimfU-rAIZLDA

HTTP/1.x 200 OK
Content-Type: text/html; charset=UTF-8
Cache-Control: public,max-age=600
Server: TrustRank Frontend
Content-Length: 0
Date: Fri, 29 Feb 2008 12:46:36 GMT
----------------------------------------------------------
https://addons.mozilla.org/ja/firefox/downloads/file/13583/minkaku-1.3-fx.xpi

GET /ja/firefox/downloads/file/13583/minkaku-1.3-fx.xpi HTTP/1.1
Host: addons.mozilla.org
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; ja; rv:1.8.1.12) Gecko/20080201 Firefox/2.0.0.12
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language: ja,en-us;q=0.7,en;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: Shift_JIS,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Cookie: __utmz=164683759.1204289207.7.6.utmccn=(referral)|utmcsr=mozilla-japan.org|utmcct=/addons/firefox/|utmcmd=referral; __utma=164683759.1355901390.1204227280.1204283674.1204289207.7; __utmb=164683759; __utmc=164683759
If-Modified-Since: Fri, 29 Feb 2008 12:43:41 GMT

HTTP/1.x 304 Not Modified
Connection: Keep-Alive
Date: Fri, 29 Feb 2008 12:43:32 GMT
Via: NS-CACHE-6.0: 4
Age: 177
Expires: Fri, 29 Feb 2008 13:43:41 GMT
Cache-Control: max-age=3600

この状態から、LANケーブルを外し無線LANで接続時

https://addons.mozilla.org/ja/firefox/downloads/file/13583/minkaku-1.3-fx.xpi

GET /ja/firefox/downloads/file/13583/minkaku-1.3-fx.xpi HTTP/1.1
Host: addons.mozilla.org
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; ja; rv:1.8.1.12) Gecko/20080201 Firefox/2.0.0.12
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language: ja,en-us;q=0.7,en;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: Shift_JIS,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Cookie: __utmz=164683759.1204282351.4.4.utmccn=(referral)|utmcsr=mozilla-japan.org|utmcct=/addons/firefox/|utmcmd=referral; __utma=164683759.1355901390.1204227280.1204282351.1204283070.5; __utmb=164683759; __utmc=164683759

HTTP/1.x 302 Found
Age: 0
Date: Fri, 29 Feb 2008 11:04:44 GMT
Expires: Fri, 29 Feb 2008 12:04:53 GMT
Cache-Control: max-age=3600 ,public
Connection: Keep-Alive
Via: NS-CACHE-6.0: 4
Server: Apache/2.0.52 (Red Hat)
X-Powered-By: PHP/4.3.9
X-AMO-ServedBy: mrapp10
Last-Modified: Fri, 29 Feb 2008 11:04:53 GMT
Location: http://releases.mozilla.org/pub/mozilla.org/addons/4562/minkaku-1.3-fx.xpi
Content-Length: 0
Content-Type: text/html; charset=UTF-8
----------------------------------------------------------
http://releases.mozilla.org/pub/mozilla.org/addons/4562/minkaku-1.3-fx.xpi

GET /pub/mozilla.org/addons/4562/minkaku-1.3-fx.xpi HTTP/1.1
Host: releases.mozilla.org
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; ja; rv:1.8.1.12) Gecko/20080201 Firefox/2.0.0.12
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language: ja,en-us;q=0.7,en;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: Shift_JIS,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive

HTTP/1.x 200 OK
Date: Fri, 29 Feb 2008 11:04:53 GMT
Server: Apache
Last-Modified: Mon, 26 Mar 2007 20:37:59 GMT
Accept-Ranges: bytes
Content-Length: 6819
Cache-Control: max-age=600
Expires: Fri, 29 Feb 2008 11:14:53 GMT
Connection: close
Content-Type: application/x-xpinstall
----------------------------------------------------------
https://addons.mozilla.org/ja/firefox/downloads/file/13583/minkaku-1.3-fx.xpi

GET /ja/firefox/downloads/file/13583/minkaku-1.3-fx.xpi HTTP/1.1
Host: addons.mozilla.org
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; ja; rv:1.8.1.12) Gecko/20080201 Firefox/2.0.0.12
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language: ja,en-us;q=0.7,en;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: Shift_JIS,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Cookie: __utmz=164683759.1204282351.4.4.utmccn=(referral)|utmcsr=mozilla-japan.org|utmcct=/addons/firefox/|utmcmd=referral; __utma=164683759.1355901390.1204227280.1204282351.1204283070.5; __utmb=164683759; __utmc=164683759
If-Modified-Since: Fri, 29 Feb 2008 11:04:53 GMT

HTTP/1.x 304 Not Modified
Connection: Keep-Alive
Date: Fri, 29 Feb 2008 11:04:44 GMT
Via: NS-CACHE-6.0: 4
Age: 17
Expires: Fri, 29 Feb 2008 12:04:53 GMT
Cache-Control: max-age=3600
----------------------------------------------------------
http://releases.mozilla.org/pub/mozilla.org/addons/4562/minkaku-1.3-fx.xpi

GET /pub/mozilla.org/addons/4562/minkaku-1.3-fx.xpi HTTP/1.1
Host: releases.mozilla.org
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; ja; rv:1.8.1.12) Gecko/20080201 Firefox/2.0.0.12
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language: ja,en-us;q=0.7,en;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: Shift_JIS,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Range: bytes=4096-
If-Range: Mon, 26 Mar 2007 20:37:59 GMT

HTTP/1.x 206 Partial Content
Date: Fri, 29 Feb 2008 11:05:10 GMT
Server: Apache
Last-Modified: Mon, 26 Mar 2007 20:37:59 GMT
Accept-Ranges: bytes
Content-Length: 2723
Cache-Control: max-age=600
Expires: Fri, 29 Feb 2008 11:15:10 GMT
Content-Range: bytes 4096-6818/6819
Connection: close
Content-Type: application/x-xpinstall
----------------------------------------------------------
http://sb.google.com/safebrowsing/update?client=navclient-auto-ffox&appver=2.0.0.12&version=goog-white-domain:1:29,goog-white-url:1:371,goog-black-url:1:18905,goog-black-enchash:1:45633

GET /safebrowsing/update?client=navclient-auto-ffox&appver=2.0.0.12&version=goog-white-domain:1:29,goog-white-url:1:371,goog-black-url:1:18905,goog-black-enchash:1:45633 HTTP/1.1
Host: sb.google.com
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; ja; rv:1.8.1.12) Gecko/20080201 Firefox/2.0.0.12
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language: ja,en-us;q=0.7,en;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: Shift_JIS,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Cookie: PREF=ID=4c158eb9579238bf:TM=1204282835:LM=1204282835:S=mukcimfU-rAIZLDA

HTTP/1.x 200 OK
Content-Type: text/html; charset=UTF-8
Cache-Control: public,max-age=600
Server: TrustRank Frontend
Content-Length: 0
Date: Fri, 29 Feb 2008 11:07:12 GMT
----------------------------------------------------------

長文失礼しました