I run WP 3.3.1 with newest wp-piwik plugin and newest Piwik software as a multisite installation (sub blogs in subdirectories), where these sub blogs are mapped to subdomains. I have deactivated all other plugins and tested it with WP standard theme.
The plugin is NOT (!) activated as network, but only in - for the moment - in the main blog!
When I try to change the settings there of wp-piwik I get an error "unknow site/blog".
I tried your test script here:
and it gives me the result:
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<p>You don't have permission to access /statistik//
on this server.</p>
Is it really right, that there is a double slash behind "/statistik"?
Maybe this is causing the error?
Because in my test script I have added just this:
$strPiwikURL = 'http://xxxxx.de/statistik';