Piwik doesn't load



since yesterday Piwik doesn’t load anymore.
If I access the index.php of Piwik I’ll be redirected to
But I get the browser error “no data recieved”:
Error 324 (net::ERR_EMPTY_RESPONSE)

How could that be? How could I fix that?
I didn’t change anything at Piwik.


After a server restart it works again.