Hi, I ran into a set of issues on a server and determined that it was definitely WP-Piwik. It only happens on this server.
Once the plugin is enabled, the site would take about 12 seconds to load, and would be nearly impossible to get into the WP-Piwik settings in the Admin panel.
I know that this is only on one server, so it's not necessarily your fault, but you can feel free to contact me if you'd like an account on this server to test what is happening. Others might bump into the issue. It's a high-end shared host that normally runs VERY fast.
Or perhaps there's some extra debugging tha I'm mising?