Creaste el htaccess en la carpeta de tu foro con los datos correspondientes?.
Te recomiendo uno asi:
Código:
RewriteEngine on
RewriteBase /foro/
# Google SEO workaround for search.php highlights:
RewriteRule ^([^&]*)&(.*)$ http://inu-sekai.com.ar/foro/$1?$2 [L,QSA,R=301]
# Google SEO Sitemap:
RewriteRule ^sitemap-([^./]+)\.xml$ misc.php?google_seo_sitemap=$1 [L,QSA,NC]
# Google SEO URL Forums:
RewriteRule ^Forum-([^./]+)$ forumdisplay.php?google_seo_forum=$1 [L,QSA,NC]
# Google SEO URL Threads:
RewriteRule ^Thread-([^./]+)$ showthread.php?google_seo_thread=$1 [L,QSA,NC]
# Google SEO URL Announcements:
RewriteRule ^Announcement-([^./]+)$ announcements.php?google_seo_announcement=$1 [L,QSA,NC]
# Google SEO URL Users:
RewriteRule ^User-([^./]+)$ member.php?action=profile&google_seo_user=$1 [L,QSA,NC]
# Google SEO URL Calendars:
RewriteRule ^Calendar-([^./]+)$ calendar.php?google_seo_calendar=$1 [L,QSA,NC]
# Google SEO URL Events:
RewriteRule ^Event-([^./]+)$ calendar.php?action=event&google_seo_event=$1 [L,QSA,NC]
# Google SEO 404:
ErrorDocument 404 /foro/misc.php?google_seo_error=404
# Default MyBB Rewrite Rules:
RewriteRule ^forum-([0-9]+)\.html$ forumdisplay.php?fid=$1 [L,QSA]
RewriteRule ^forum-([0-9]+)-page-([0-9]+)\.html$ forumdisplay.php?fid=$1&page=$2 [L,QSA]
RewriteRule ^thread-([0-9]+)\.html$ showthread.php?tid=$1 [L,QSA]
RewriteRule ^thread-([0-9]+)-page-([0-9]+)\.html$ showthread.php?tid=$1&page=$2 [L,QSA]
RewriteRule ^thread-([0-9]+)-lastpost\.html$ showthread.php?tid=$1&action=lastpost [L,QSA]
RewriteRule ^thread-([0-9]+)-nextnewest\.html$ showthread.php?tid=$1&action=nextnewest [L,QSA]
RewriteRule ^thread-([0-9]+)-nextoldest\.html$ showthread.php?tid=$1&action=nextoldest [L,QSA]
RewriteRule ^thread-([0-9]+)-newpost\.html$ showthread.php?tid=$1&action=newpost [L,QSA]
RewriteRule ^thread-([0-9]+)-post-([0-9]+)\.html$ showthread.php?tid=$1&pid=$2 [L,QSA]
RewriteRule ^post-([0-9]+)\.html$ showthread.php?pid=$1 [L,QSA]
RewriteRule ^announcement-([0-9]+)\.html$ announcements.php?aid=$1 [L,QSA]
RewriteRule ^user-([0-9]+)\.html$ member.php?action=profile&uid=$1 [L,QSA]
RewriteRule ^calendar-([0-9]+)\.html$ calendar.php?calendar=$1 [L,QSA]
RewriteRule ^calendar-([0-9]+)-year-([0-9]+)\.html$ calendar.php?action=yearview&calendar=$1&year=$2 [L,QSA]
RewriteRule ^calendar-([0-9]+)-year-([0-9]+)-month-([0-9]+)\.html$ calendar.php?calendar=$1&year=$2&month=$3 [L,QSA]
RewriteRule ^calendar-([0-9]+)-year-([0-9]+)-month-([0-9]+)-day-([0-9]+)\.html$ calendar.php?action=dayview&calendar=$1&year=$2&month=$3&day=$4 [L,QSA]
RewriteRule ^calendar-([0-9]+)-week-(n?[0-9]+)\.html$ calendar.php?action=weekview&calendar=$1&week=$2 [L,QSA]
RewriteRule ^event-([0-9]+)\.html$ calendar.php?action=event&eid=$1 [L,QSA]
Recuerda configurar bien el
RewriteBase con la carpeta donde esta el foro y en
# Default MyBB Rewrite Rules debes poner la URL completa de tu web.
Saludos!.