ust to be sure, I set up your redirect locally:

<VirtualHost *:80>
DirectoryIndex index.html index.php
DocumentRoot E:/temp
<Directory "E:/temp">
Order Allow,Deny
Allow from
<VirtualHost *:80>
RedirectMatch permanent ^/(.*)$1


Redirecting back to the same server, it works perfectly. Since I can’t see your actual domain, I can’t look at your DNS situation, but if you’re absolutely sure you have no other redirects on the www server, that’s where I’d look: dig those 2 domains. www might not be where you think it is, or DNS might be pointing all subdomains at the root domain.

Another possibility is that your contains something like the following.

Header( "HTTP/1.1 301 Moved Permanently" ); 
Header( "Location:" ); 

Also… check WORDPRESS options … maybe is a WWW site