Cannot enable contacts app


I am unable to enable the contacts, calender and documents apps. After a while I receive a “cURL error 52: Empty reply from server” error.
Any hints what I am doing wrong?


And now it works… I didn’t change anything… But it works. How can I mark this as solved?

What was the solution? Preferably, post the solution first before marking it as solved to help others who might have this problem. Then, click the checkbox button to the left of the “reply” button on the reply that solved the problem.