Work-around found!
just comment in CF7DBPlugin.php:
Starting at line 653
[Code moderated as per the Forum Rules. Please use the pastebin]
Error in the apache2 log:
[Wed Jan 25 11:05:06 2012] [error] [client <IP-ADDRESS>] PHP Fatal error: Call to undefined function is_plugin_active() in /<PATH>/wp-content/plugins/contact-form-7-to-database-extension/CF7DBPlugin.php on line 653, referer: http://<HOST>
Any ideas?
