On September 30th, 2011, an incorrect detection for PWS:Win32/Zbot was identified and as a result, Google Chrome was inadvertently blocked and in some cases removed. Within a few hours, Microsoft released an update that addresses the issue. Signature versions 1.113.672.0 and higher include this update. Affected customers should manually update Microsoft Security Essentials with the latest signatures. After updating the definitions, reinstall Google Chrome. We apologize for the inconvenience this may have caused our customers.