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Upgrade from DNN 7.0.6 to 7.1.1 -- no install errors. The Could not load file or assembly 'FileHelpers, ... error is present when trying to select page settings, page appearance, page permissions from edit page drop down; site settings & file management.
Server is running Windows 2008, IIS 7 & SQL Server 2008. Site is using AppPool .NET 4.0, integrated.
Everything works fine before the upgrade.