Problem loading data

Hey there.
We have a problem in our Piwik installation.
Loading the data via AJAX does not work for our most frequent visited site.
Just the notification “loading data” appears.

For this example I opened Visitor->Overview
Last and only action in my firebug Console is this:
http: //
The line of this request is marked in red in my firebug console.
Calling this URL in my browser directly I only get a blank page, no response (after waiting some seconds).

Do you have any Idea?

Problem appears only on this page.

Regards from Germany

Found solution by myself
In default configuration PHP has max_runtime = 60 and memory_limit = 128
Increased both and now it works