Can't login to admin, can't login as customer, cart empty

Hi,

I'm suddenly having huge problems with my Opencart.
I can't login to the admin panel. It doesn't show any errors it just doesn't log me in.
Also I noticed, that the cart doesn't work anymore. at first it says the product is added, but it still displays the cart as empty when I click it.
I also can't log in as a customer.

It seem like some sort of cookie problem. I have no idea what to do or where to search for the problem, because I'm not getting any error messages.

You can visit my shop here to see for yourself: http://shop.gassmannzuerich.ch

Has anyone encountered this problem before?

Best Regards
Kaethen

Does the same happen with the default template ?

I can't change the templates because I can't log in to the admin panel, so I can't try...

seems to be working now for me

Any chance you can post the solution applied?