[FBChris]

Upgrading to Apache 2.x is no really possible at the moment. Maybe in a later stage.

For now I have found some information on http://www.vbsupport.org/forum/showthread.php?t=32958. Its in Russian, with Google translate I found out a little bit more...

This error occurs due to that apache 1.3 uses POSIX ERE and apache 2.x uses REGEX. The errors is specifically in the non-capturing clusters "(?: exp)" which is not supported by POSIX ERE or apache 1.3

With some copy and paste from various sources I have come up with a working .htaccess in my Apache 1.3 environment.

RewriteEngine On

# If you are having problems or are using VirtualDocumentRoot, uncomment this line and set it to your vBulletin directory.
# RewriteBase /forum/

RewriteCond %{REQUEST_FILENAME} -s [OR]
RewriteCond %{REQUEST_FILENAME} -l [OR]
RewriteCond %{REQUEST_FILENAME} -d

RewriteRule ^.*$ - [NC,L]

RewriteRule ^threads/.* showthread.php [QSA]
RewriteRule ^forums/.* forumdisplay.php [QSA]
RewriteRule ^members/.* member.php [QSA]
RewriteRule ^blogs/.* blog.php [QSA]
ReWriteRule ^entries/.* entry.php [QSA]
RewriteRule ^list/([^/]*/)([0-9]+) list.php?r=$1$2&%{QUERY_STRING}
RewriteRule ^content/(.*) content.php?r=$1&%{QUERY_STRING}
RewriteRule ^widget/config/([0-9]+) widget.php?r=config/$1&%{QUERY_STRING}

RewriteCond %{REQUEST_FILENAME} -s [OR]
RewriteCond %{REQUEST_FILENAME} -l [OR]
RewriteCond %{REQUEST_FILENAME} -d

RewriteRule ^.*$ - [NC,L]

RewriteRule ^$ $1.php?r=$2 [QSA]