Hello Mat,
this is pure Virtuemart settings. At your virtuemart template settings (VirtueMart -> Admin -> Configuration -> Site -> Select the theme for your Shop .... Configuration ) please turn off AJAX add to cart (Use Ajax to add, update or delete products from the cart?) if you want your customers to redirect directly to the cart after they click it. If you have any javascript errors in your template this is a risky way of using add to cart as various versions of IE handle errors differently and you might not be able to provide a functional site to some customers of certain IE versions. Have a look into FireFox Error Console to see if your site is javascript error free so you can safely use AJAX cart or not. For AJAX to work properly it is recommended to use only one domain for requests so your site does not make cross domain requests which are blocked by many browsers (called XSS attacks). This can be done by modification of htaccess so your domain from
http://domain.com/ gets redirected to
http://www.domain.com/ If this modification does not work, you might investigate this redirect in your SEO component settings or vhost settings. Htaccess redirect is much more safe and much faster than php redirect from SEO component.
Second part of your problem: you get redirected to the frontpage after signing in at the checkout page. To fix this try different configurations of your virtuemart login module or eventually disable login feature at the checkout page in the configurator display tab. We will work on this issue later on, so we don't rely on virtuemart login module.
Hopes this helps,
Regards,
Stan Scholtz, RuposTel s.r.o.