404 error/problem/message with bbpress and WP

I posted this over at the bbPress-forum, but seen no input there so far, so I put it here as well and hope for your bright and enligting input! ??

* * * *
I have WP and BBPress integrated with BB in a subdirectory. Now I found a strange thing in Firebug’s “Net” section (where Firebug shows “requests”).
When I load anything WP-realted everything looks fine, but when I load something BB-related HTML-request is listed with (404) in Firebug, although the page loads just fine.

URL to the blog is https://www2.enserio.se/blogg/
and the forum is at
https://www2.enserio.se/blogg/forumet/

I’ve had a problem when trying to check the forum at https://www.websiteoptimization.com/, which says that the page (and any other BB-realted page) doesn’t exist and report a 404-error. Somehow I thing it’s related to the Firebug-thing.

I suspect it’s an ‘htaccess’ related problem, but I can’t figure out how to fix it. The htaccess in the WP root is:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /blogg/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /blogg/index.php [L]
</IfModule>
# END WordPress

and dito in the bb root is:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /blogg/forumet/
RewriteRule ^forum/(.+)/page/([0-9]+)$ /blogg/forumet/forum.php?id=$1&page=$2 [L,QSA]
RewriteRule ^forum/(.+)/?$ /blogg/forumet/forum.php?id=$1 [L,QSA]
RewriteRule ^topic/(.+)/page/([0-9]+)$ /blogg/forumet/topic.php?id=$1&page=$2 [L,QSA]
RewriteRule ^topic/(.+)/?$ /blogg/forumet/topic.php?id=$1 [L,QSA]
RewriteRule ^tags/(.+)/page/([0-9]+)$ /blogg/forumet/tags.php?tag=$1&page=$2 [L,QSA]
RewriteRule ^tags/(.+)/?$ /blogg/forumet/tags.php?tag=$1 [L,QSA]
RewriteRule ^tags/?$ /blogg/forumet/tags.php [L,QSA]
RewriteRule ^profile/(.+)/page/([0-9]+)$ /blogg/forumet/profile.php?id=$1&page=$2 [L,QSA]
RewriteRule ^profile/(.+)/([a-z-]+)$ /blogg/forumet/profile.php?id=$1&tab=$2 [L,QSA]
RewriteRule ^profile/(.+)/([a-z-]+)/page/([0-9]+)$ /blogg/forumet/profile.php?id=$1&tab=$2&page=$3 [L,QSA]
RewriteRule ^profile/(.+)/?$ /blogg/forumet/profile.php?id=$1 [L,QSA]
RewriteRule ^view/([a-z-]+)/page/([0-9]+)$ /blogg/forumet/view.php?view=$1&page=$2 [L,QSA]
RewriteRule ^view/([a-z-]+)$ /blogg/forumet/view.php?view=$1 [L,QSA]
RewriteRule ^rss/$ /blogg/forumet/rss.php [L,QSA]
RewriteRule ^rss/forum/([0-9]+)$ /blogg/forumet/rss.php?forum=$1 [L,QSA]
RewriteRule ^rss/topic/([0-9]+)$ /blogg/forumet/rss.php?topic=$1 [L,QSA]
RewriteRule ^rss/tags/([a-z-]+)$ /blogg/forumet/rss.php?tag=$1 [L,QSA]
RewriteRule ^rss/profile/([0-9]+)$ /blogg/forumet/rss.php?profile=$1 [L,QSA]
RewriteRule ^mlist/ mlist.php? [L,QSA]
</IfModule>

I can’t use the “Options +MultiViews” in the bbPress htaccess, gives me an “Internal server error”.

If I set WP permalinks to default these problems disapear, but I don’t want do do that …

Any input on this is most welcome!