Earlier this month Microsoft released Windows Management Framework 3.0 for Windows 2008 SP2, Windows 2008 R2 SP1 and Windows 7 SP1.
The update includes PowerShell 3.0, which is not currently compatible with Exchange 2007 or Exchange 2010.
The current advice from Microsoft is to not install this patch on systems running Exchange 2007 and Exchange 2010. This includes SBS 2008 and SBS 2011.
KB2506146 refers to Windows 2008 SP2
KB2506143 refers to Windows 2008 R2 SP1 and Windows 7 SP1
From the Exchange Team blog: http://blogs.technet.com/b/exchange/archive/2012/12/14/windows-management-framework-3-0-on-exchange-2007-and-exchange-2010.aspx
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