After Piwik-Update to 2.0 - Magento doesn't work (no replies)

Hello!

I have a strange problem with Piwik!
When I perform the automatic update, the Magento shop is no longer running.
In the frontend and backend Magento goes into the installation mode.

This is the error.log:

PHP Warning: simplexml_load_file() [<a href='function.simplexml-load-file'>function.simplexml-load-file</a>]: I/O warning : failed to load external entity &quot;/home/weinwelt/public_html/shop/app/etc/local.xml&quot; in /home/weinwelt/public_html/shop/app/Mage.php on line 766
[17-Dec-2013 17:00:02 UTC] PHP Notice: Trying to get property of non-object in /home/weinwelt/public_html/shop/app/Mage.php on line 768
[17-Dec-2013 17:00:02 UTC] PHP Notice: Trying to get property of non-object in /home/weinwelt/public_html/shop/app/Mage.php on line 768
[17-Dec-2013 17:00:02 UTC] PHP Notice: Trying to get property of non-object in /home/weinwelt/public_html/shop/app/Mage.php on line 768

local.xml was not changed.
Only when I do a restore of the data before the date of the update everything is ok.

Even if I completely re-install Piwik in a different folder, it comes with the installation routine of Piwik back to the problem.

Very mysterious!