Manage Resources crashed after upgrading

[LukasGr.]

Hi guys,

I just upgraded to 4.0.0 as everyone was saying that they upgraded without any issues. That's true for most of the parts, but there is one big critical error on my site. I had my own design based on the standard template and if its enabled now the whole site is broken. If I wanna check the resource i get this:

Do you have an idea! It's pretty bad - ned help.