Checkout module hides all content

[Somepub]

I recently bought a One Step Checkout / One Page Checkout module.

And testing with register account, checkout worked out fine!

But here is the weird behavior.. when trying to check out without logged in(as guest), it puts all page elements to display:none

 

 

So first I thought It could be an error, but when enableing DEVMODE it didn't show any errors, no php nor js errors. It just hides all elements.

What could be the issue?