Advanced seo mod,problema .htaccess,errore 404 quando si scrive un topic.

Salve a tutti,spero mi possiate dare una mano.
Ho installato la advanced mod rewrite,ma ho un problema, quando creo o rispondo ad un nuovo topic mi da errore 404,perchè c'è una cartella phpbb di mezzo all'indirizzo che sul forum non esiste...
per essere piu precisi..

mioforum.altervista.org/phpbb/posting.php?mode=reply&f=27&t=5873

Il mio forum non sta in nessuna cartella phpbb quindi non so come possa esserci quest'errore...
Il file. htaccess questo è

 # Lines That should already be in your .htacess
<Files "config.php">
Order Allow,Deny
Deny from All
</Files>
<Files "common.php">
Order Allow,Deny
Deny from All
</Files>

# You may need to un-comment the following lines
# Options +FollowSymlinks
# To make sure that rewritten dir or file (/|.html) will not load dir.php in case it exist
# Options -MultiViews
# REMEBER YOU ONLY NEED TO STARD MOD REWRITE ONCE
RewriteEngine On
# REWRITE BASE
RewriteBase /
# HERE IS A GOOD PLACE TO FORCE CANONICAL DOMAIN

# DO NOT GO FURTHER IF THE REQUESTED FILE / DIR DOES EXISTS
RewriteCond %{REQUEST_FILENAME} -f
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule . - [L]
#####################################################
# PHPBB  SEO REWRITE RULES ALL MODES
#####################################################
# AUTHOR : dcz phpbb-seo.com
# STARTED : 01/2006
#################################
# FORUMS PAGES
###############
# FORUM INDEX
RewriteRule ^forum\.html$ /index.php [QSA,L,NC]
# FORUM ALL MODES
RewriteRule ^(forum|[a-z0-9_-]*-f)([0-9]+)/?(page([0-9]+)\.html)?$ /viewforum.php?f=$2&start=$4 [QSA,L,NC]
# TOPIC WITH VIRTUAL FOLDER ALL MODES
RewriteRule ^(forum|[a-z0-9_-]*-f)([0-9]+)/(topic|[a-z0-9_-]*-t)([0-9]+)(-([0-9]+))?\.html$ /viewtopic.php?f=$2&t=$4&start=$6 [QSA,L,NC]
# GLOBAL ANNOUNCES WITH VIRTUAL FOLDER ALL MODES
RewriteRule ^announces/(topic|[a-z0-9_-]*-t)([0-9]+)(-([0-9]+))?\.html$ /viewtopic.php?t=$2&start=$4 [QSA,L,NC]
# TOPIC WITHOUT FORUM ID & DELIM ALL MODES
RewriteRule ^([a-z0-9_-]*)/?(topic|[a-z0-9_-]*-t)([0-9]+)(-([0-9]+))?\.html$ /viewtopic.php?forum_uri=$1&t=$3&start=$5 [QSA,L,NC]
# PHPBB FILES ALL MODES
RewriteRule ^resources/[a-z0-9_-]+/(thumb/)?([0-9]+)$ /download/file.php?id=$2&t=$1 [QSA,L,NC]
# PROFILES ALL MODES WITH ID
RewriteRule ^(member|[a-z0-9_-]*-u)([0-9]+)\.html$ /memberlist.php?mode=viewprofile&u=$2 [QSA,L,NC]
# USER MESSAGES ALL MODES WITH ID
RewriteRule ^(member|[a-z0-9_-]*-u)([0-9]+)-(topics|posts)(-([0-9]+))?\.html$ /search.php?author_id=$2&sr=$3&start=$5 [QSA,L,NC]
# GROUPS ALL MODES
RewriteRule ^(group|[a-z0-9_-]*-g)([0-9]+)(-([0-9]+))?\.html$ /memberlist.php?mode=group&g=$2&start=$4 [QSA,L,NC]
#  POST
RewriteRule ^post([0-9]+)\.html$ /viewtopic.php?p=$1 [QSA,L,NC]
# ACTIVE TOPICS
RewriteRule ^active-topics(-([0-9]+))?\.html$ /search.php?search_id=active_topics&start=$2&sr=topics [QSA,L,NC]
# UNANSWERED TOPICS
RewriteRule ^unanswered(-([0-9]+))?\.html$ /search.php?search_id=unanswered&start=$2&sr=topics [QSA,L,NC]
# NEW POSTS
RewriteRule ^newposts(-([0-9]+))?\.html$ /search.php?search_id=newposts&start=$2&sr=topics [QSA,L,NC]
# THE TEAM
RewriteRule ^the-team\.html$ /memberlist.php?mode=leaders [QSA,L,NC]
# HERE IS A GOOD PLACE TO ADD OTHER PHPBB RELATED REWRITERULES

# FORUM WITHOUT ID & DELIM ALL MODES (SAME DELIM)
# THESE THREE LINES MUST BE LOCATED AT THE END OF YOUR HTACCESS TO WORK PROPERLY
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^([a-z0-9_-]+)/?(page([0-9]+)\.html)?$ /viewforum.php?forum_uri=$1&start=$3 [QSA,L,NC]
# FIX RELATIVE PATHS : FILES
RewriteRule ^.+/(style\.php|ucp\.php|mcp\.php|faq\.php|download/file.php)$ /$1 [QSA,L,NC,R=301]
# FIX RELATIVE PATHS : IMAGES
RewriteRule ^.+/(styles/.*|images/.*)/$ /$1 [QSA,L,NC,R=301]
# END PHPBB PAGES
#####################################################

Avete consigli o soluzioni?? ve ne sarei davvero grato.