After you updated a server that is running SBS 2011 Essentials, Windows Storage Server 2008 R2 Essentials or Windows Home Server 2011 with the Update Rollup 2, you receive the warning "Computer Monitoring Error" in the Launchpad or Dashboard.

Please visit the following post for the resolution.

http://blogs.technet.com/b/sbs/archive/2012/02/29/computer-monitoring-error-in-dashboard-or-launchpad-of-sbs-2011-essential-servers.aspx