Website went down after installing MarketPress eCommerce

The website is in maintainance while I installed MarketPress eCommerce. After the setup I started to add a product, but when I tried to publish it the whole site is "gone".. Cant access it or see it on my domain.

The strange thing is that the maintainance link work:

But when I go to my main domain or WP-Admin I just get "redirected" to my domainregistrar where I also got my webhotel (look at the links below):