Hi,
There is a known issue on Microsoft Exchange Server 2010 if it's installed on systems that run .NET Framework 4.5 (or higher). The powershell cmdlets stop working and the only workaround is to uninstall all .NET Framework versions (4.5 or higher) and repair the .NET Framework 4.0 installation. Do not do this on Windows Server 2012 (or higher) as this will break your operating system.
This bug was acknowledged by Microsoft however the official bug report got deleted so here is a cached copy: https://web.archive.org/web/20121129073751/http://connect.microsoft.com/VisualStudio/feedback/details/770748/powershell-exception-after-4-5-upgrade
Exchange 2007, 2013 and 2016 are not affected by this bug.
Chris