I am running PHP version 5.4.19 (confirmed with phpinfo). After updating to the latest version of the plugin, when I try to access the admin area, I get the following error:
Parse error: syntax error, unexpected T_STRING in /wp-content/plugins/wp-piwik/wp-piwik.php on line 751
Also, I have the following line in my .htaccess file:
addhandler x-httpd-php5-cgi .php
I had to disable FastCGI for some reason that currently escapes me.