Hi,
In the Global Configuration of joomla in SEO Settings
If i set: Search Engine Friendly URLs to Yes or set URL rewriting to Yes,
i will have a problem in the checkout.
Both buttons, register and checkout or checkout as guest when clicked, the pop up opens but shows nothing and,
redirect to the jooma user login component.
I would be very glad if someone, can help me with that.

Hi,

Please read this post.
www.flexiblewebdesign.com/forum-virtuemart-2-template-puremart-support/542-register-and-checkout-popup-goes-to-joomla-login#2261

The same exact question has been asked and the issue has been resolved.

Regards.