[Skyrider]

Not sure if you've done the spacings on your rewrite rule on purpose, but:

http://www.unix.com/web-programming/...etin-urls.html

After uninstallation you can also redirect your indexed content to original vBulletin urls. Please carefully check the rewrite rules and use the one that fits your current url structure.

RewriteEngine on
RewriteRule [^/]+/([0-9]+)-[^/]+\.html http://www.domain.com/forums/showthread.php?t=$1 [L,R=301]

If you have your thread rewrite rules set as forum-name/threadname-threadid.html use the following .htaccess

RewriteEngine on
RewriteRule [^/]+/[^/]+-([0-9]+)\.html http://www.domain.com/forums/showthread.php?t=$1 [L,R=301]

If you have your thread rewrite rules set as forum-name/threadname-threadid/ use the following .htaccess

RewriteEngine on
RewriteRule [^/]+/[^/]+-([0-9]+)/ http://www.domain.com/forums/showthread.php?t=$1 [L,R=301]

This however will not work if you are using nginx. Only works with apache.