If you click on Enterprise Instant Messenger module tool Manage Server Policies and get the following error:

[TypeLoadException: Could not load type 'System.Runtime.Versioning.TargetFrameworkAttribute' from assembly 'mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.]
   System.ModuleHandle.ResolveType(Int32 typeToken, RuntimeTypeHandle* typeInstArgs, Int32 typeInstCount, RuntimeTypeHandle* methodInstArgs, Int32 methodInstCount) +0
   System.ModuleHandle.ResolveTypeHandle(Int32 typeToken, RuntimeTypeHandle[] typeInstantiationContext, RuntimeTypeHandle[] methodInstantiationContext) +227
   System.Reflection.Module.ResolveType(Int32 metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments) +355
   System.Reflection.CustomAttribute.FilterCustomAttributeRecord(CustomAttributeRecord caRecord, MetadataImport scope, Assembly& lastAptcaOkAssembly, Module decoratedModule, MetadataToken decoratedToken, RuntimeType attributeFilterType, Boolean mustBeInheritable, Object[] attributes, IList derivedAttributes, RuntimeType& attributeType, RuntimeMethodHandle& ctor, Boolean& ctorHasParameters, Boolean& isVarArg) +474
   System.Reflection.CustomAttribute.IsCustomAttributeDefined(Module decoratedModule, Int32 decoratedMetadataToken, RuntimeType attributeFilterType, Boolean mustBeInheritable) +630
   System.Reflection.CustomAttribute.IsDefined(Assembly assembly, RuntimeType caType) +138
   System.Data.Metadata.Edm.ObjectItemCollection.IsSchemaAttributePresent(Assembly assembly) +38
   System.Data.Metadata.Edm.ObjectItemCollection.LoadAssemblyFromCache(ObjectItemCollection objectItemCollection, Assembly assembly, Boolean loadReferencedAssemblies) +249
   System.Data.Metadata.Edm.ObjectItemCollection.LoadFromAssembly(Assembly assembly) +85

or another error related to System.Core, the issue is actually related to the Dashboards update.

For the latest Dashboards update, files were moved from the bin folder of the portal to the ClientBin folder of the Dashboards module.

These are the files that should be removed from the Production Portal\bin folder:

AppManifest.xaml
ComponentArt.Silverlight.DataVisualization.Charting.dll
ComponentArt.Silverlight.DataVisualization.Common.dll
ComponentArt.Silverlight.DataVisualization.Gauges.dll
ComponentArt.Silverlight.DataVisualization.lic
SilverlightVisualizationViewer.dll
SilverlightVisualizationViewer.xap

After that, the page should load without error.