After installation of the Pronestor Planner add-in for Microsoft Outlook 2010 - the add-in does not load and the following message is shown:
"The following solution cannot be loaded because Microsoft Office support for the .NET Framework 3.5 is not installed. PronestorOutlook.2007Addin.vsto|vstolocal. For more information see http://...."
The VSTO for Office 2010 (VSTOR 2010) has not been initialized properly - this is a known issue from Microsoft
How to solve
For 32-bit editions of Microsoft Windows OS - http://go.microsoft.com/fwlink/?LinkId=158917
For 64-bit editions of Microsoft Windows OS - http://go.microsoft.com/fwlink/?LinkId=158918
Microsoft Office 2010 Primary Interop Assembly (Download from MS)