non-www redirect to www

[Kesha]

Hi all,

I know that this should be a trivial issue with simple resolution, however we're not completely sure what's going on at the moment. I'm also not sure if this belongs on vB.org or vB.com, but I figured I'd start here and move if necessary.

We run vBulletin 4.2.3 + vBSEO. We upgraded to 4.2.3 the day it was released. There have been no reported instances of this occurring until now... That I'm aware of.

It's recently been brought to my attention that when a user visits our site via http://example.com/forums, it does not redirect to http://www.example.com as it is supposed to. I was under the impression that all the URL rewriting was done by vBSEO (and to an extent, it is), however it no longer seems to be rewriting just /forums/. vBSEO still happily rewrites anything non-www like http://example.com/forums/valid-forum-name to www.example.com/forums/valid-forum-name/ without issue.

I tried adding this line to .htaccess to fix the issue:

RewriteCond %{HTTP_HOST} !^www\.
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]

... When I visit http://example.com/forums with that line in .htaccess, it redirects to http://www.example.com/ but removes the forums part. When I go to something like http://example.com/forums/asdfghjklasdfghjkl, it redirects to http://www.example.com/asdfghjklasdfghjkl (removes /forums/)

When we log into the forums using the non-www URL, it posts the login to http://www.example.com/forums/login.php but then redirects back to non-www.

I'm absolutely perplexed as to why this is happening, as it hasn't been an issue until very recently. To my knowledge, nothing server-side has been changed save for a few system packages being upgraded (none affecting apache or PHP) so I'm running out of explanations as to why this might be happening.