Cannot add to cart and cannot login after htaccess change

Hi

I am having an issue where I have zencart installed in a subdirectory called mysite.com. Then I use .htaccess to rewrite the URL as follows:

RewriteCond %{HTTP_HOST} mysite\.com [NC]
RewriteCond %{REQUEST_URI} !/mysite\.com/
RewriteRule (.*) /mysite\.com/$1 [L]

The site works great with all the requests appearing to work off /. I have updated the configure.php to specify a WS url of /.

Is there a reason why I cant add items to the cart and when I login it says "There was a security error when trying to login."

Any help or pointers appreciated.

I am having an issue where I have zencart installed in a subdirectory called mysite.com. Then I use .htaccess to rewrite the URL as follows:
Why not just move ZenCart to the root of your account and dispense with the rewrite