random 404 on mod_rewrite

[piper]

Hi,

I Run a wordpress site with mod_rewrite and it's installed on the root folder

in subfolder i have a forum application and it has it's own htaccess for mod_rewrite

It works but randomly gives 404 on the forum

This is what the server have

Litespeed Enterprise 3.11, PHP 5.2.2, LSPHP 4.0

Htaccess is

RewriteEngine On
RewriteRule ^index\.html$ ./index.php?mdrw=on
RewriteRule ^manual\.html$ ./index.php?action=manual&mdrw=on
RewriteRule ^([0-9]+)_([0-9]+)_([-0-9]+)\.html$ ./index.php?action=vthread&forum=$1&topic=$2&page=$3 &mdrw=on
RewriteRule ^([0-9]+)_([-0-9]+)\.html$ ./index.php?action=vtopic&forum=$1&page=$2&mdrw=on


Any help?

Thanks in advanced