Are you running on the same server and same configuration (e.g. server software, forum version, etc) as your old website?
Any details you can share about what differs between the two sites would be appreciated
My old site is friend-arcade.com which uses Arcadem Pro which I used to do support work for. New site is friends-arcade.com which uses the pro version of vbArcade under vBulletin. Main difference is vbArcade is installed one level deep in it's own folder where Arcadem Pro is usually installed in the document root, but can be installed in deep folders if configured right.
The main difference is though, Arcadem Pro calls up arcade.php which is a small file in the root. That one calls submitscore.php which is in the /includes/ folder. The submitscore.php file returns you back to where you were but clears the session automatically.
What I think the problem lies is in the mod_rewrite. Below is the section I have in htaccess:
RewriteEngine on
# If you are having problems or are using VirtualDocumentRoot, uncomment this line and set it to your vBulletin directory.
# RewriteBase /forum/
# If you are having problems with the rewrite from content/ to content.php, uncomment this line to turn MultiViews off.
Options -MultiViews
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -l [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^.*$ - [NC,L]
# Forum
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]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -l [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^.*$ - [NC,L]
# MVC
RewriteRule ^(?
.*?)(?:/|$))(.*|$)$ $1.php?r=$2 [QSA]
# Check MVC result
RewriteCond %{REQUEST_FILENAME} -f
RewriteRule ^(.*)$ - [NC,L]
RewriteRule ^(.*)$ - [R=404,L]
The forum is the default page and only way I could get the navigation to work right in vb 4.2.