IIS7 500 Internal Server Error

In IIS7, web server 2008, I was having problems on a couple of site with authentication, so I found my way to the "Feature Delegation" page and clicked the "Reset All Delegation" link.

Now, none of my sites work. They all have an error:

500 - Internal server error.
There is a problem with the resource you are looking for, and it cannot be displayed.

Any ideas how to fix this?

I did a reboot, reset, restart etc.

thanks.