changing home url from http://x.com to http://www.x.com – solving infinite loop

hello,

I had my wordpress setup for http://x.com and needed to change it to http://www.x.com

note: is a 3.x multisite wordpress using the domain mapping plugin. all the mapped sites work well with www as I setup that in the plugin, but the main one wasnt working with www, redirecting to http://x.com

first tried some htaccess solutions like this here
RewriteCond %{HTTP_HOST} ^domain.com$ [NC]
RewriteRule ^(.*)$ http://www.domain.com/$1 [R=301,L]
and other variations with comments but that didnt work for me.

then I tried this here:
http://codex.wordpress.org/Changing_The_Site_URL
and got an infinite loop.

finally solved the infinite loop and got my site working with www modifying (adding www to the url) from all the said values, only the home field at the wp_options database table.

so, if you are stuck at some infinite loop or cannot make your domain work with www, this worked for me.

also, if from what I just explained someone realize I’m doing something wrong, I’d like to know what it is so I can fix it.

thanks!