FF 3.6.x works perfect.
It´s not possible to debugg the script because the line in which the error occurs doesn´t exist. See picture piwik-error-1.png.
If I try to use the official Piwik demosite - the same issue !!!
On some pc´s works ClamAv for Windows, no scriptblocker or firewall, on the testing system no av, no fw.
This error always occours if I click on the main menü like Dashboard, Visitors … and it seems if an ajax request state goes to an specified state, too.