Created Issue: FileLoadException in xaml designer [15215]

I have just created a new WPF project (VS2010) and added references to some assemblies required by the project, including Microsoft.Practices.ServiceLocation. Whenever I open a xaml file in the VS xaml designer, it displays the following exception:-


System.IO.FileLoadException
Could not load file or assembly 'Microsoft.Practices.ServiceLocation, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. Operation is not supported. (Exception from HRESULT: 0x80131515)
at System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)
at System.Reflection.RuntimeAssembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)
at System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection, Boolean suppressSecurityChecks)
at System.Reflection.Assembly.Load(AssemblyName assemblyRef)
at MS.Internal.Package.VSIsolationProviderService.RemoteReferenceProxy.VsReflectionResolver.GetRuntimeAssembly(Assembly reflectionAssembly)
at Microsoft.Windows.Design.Metadata.ReflectionMetadataContext.CachingReflectionResolver.GetRuntimeAssembly(Assembly reflectionAssembly)
at Microsoft.Windows.Design.Metadata.ReflectionMetadataContext.Microsoft.Windows.Design.Metadata.IReflectionResolver.GetRuntimeAssembly(Assembly reflectionAssembly)
at MS.Internal.Metadata.ClrAssembly.GetRuntimeMetadata(Object reflectionMetadata)
at Microsoft.Windows.Design.Metadata.AttributeTableContainer.<MergeAttributesIterator>d__c.MoveNext()
at Microsoft.Windows.Design.Metadata.AttributeTableContainer.GetAttributes(Assembly assembly, Type attributeType, Func`2 reflectionMapper)
at MS.Internal.Metadata.ClrAssembly.GetAttributes(ITypeMetadata attributeType)
at MS.Internal.Design.Metadata.Xaml.XamlAssembly.get_XmlNamespaceCompatibilityMappings()
at Microsoft.Windows.Design.Metadata.Xaml.XamlExtensionImplementations.GetXmlNamespaceCompatibilityMappings(IAssemblyMetadata sourceAssembly)
at Microsoft.Windows.Design.Metadata.Xaml.XamlExtensions.GetXmlNamespaceCompatibilityMappings(IAssemblyMetadata source)
at MS.Internal.Design.Metadata.ReflectionProjectNode.BuildSubsumption()
at MS.Internal.Design.Metadata.ReflectionProjectNode.SubsumingNamespace(Identifier identifier)
at MS.Internal.Design.Markup.XmlElement.BuildScope(PrefixScope parentScope, IParseContext context)
at MS.Internal.Design.Markup.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider, Boolean visitCodeModel)
at MS.Internal.Design.DocumentModel.DocumentTrees.Markup.XamlSourceDocument.FullParse(Boolean convertToXamlWithErrors)
at MS.Internal.Design.DocumentModel.DocumentTrees.Markup.XamlSourceDocument.get_RootItem()
at Microsoft.Windows.Design.DocumentModel.Trees.ModifiableDocumentTree.get_ModifiableRootItem()
at Microsoft.Windows.Design.DocumentModel.MarkupDocumentManagerBase.get_LoadState()
at MS.Internal.Host.PersistenceSubsystem.Load()
at MS.Internal.Host.Designer.Load()
at MS.Internal.Designer.VSDesigner.Load()
at MS.Internal.Designer.VSIsolatedDesigner.VSIsolatedView.Load()
at MS.Internal.Designer.VSIsolatedDesigner.VSIsolatedDesignerFactory.Load(IsolatedView view)
at MS.Internal.Host.Isolation.IsolatedDesigner.BootstrapProxy.LoadDesigner(IsolatedDesignerFactory factory, IsolatedView view)
at MS.Internal.Host.Isolation.IsolatedDesigner.BootstrapProxy.LoadDesigner(IsolatedDesignerFactory factory, IsolatedView view)
at MS.Internal.Host.Isolation.IsolatedDesigner.Load()
at MS.Internal.Designer.DesignerPane.LoadDesignerView(Boolean isReload)

System.NotSupportedException
An attempt was made to load an assembly from a network location which would have caused the assembly to be sandboxed in previous versions of the .NET Framework. This release of the .NET Framework does not enable CAS policy by default, so this load may be dangerous. If this load is not intended to sandbox the assembly, please enable the loadFromRemoteSources switch. See http://go.microsoft.com/fwlink/?LinkId=155569 for more information.

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The last paragraph seems to be a red herring as I am not loading any projects or assemblies from network shares. The entire solution and all dependent assemblies (including Service Locator) are on my local C: drive.

If I remove the project reference to Microsoft.Practices.ServiceLocation, then I can open the xaml files normally. Note also that I have not actually made use of the service locator anywhere in my code, I have merely referenced the DLL in the project. Nor have I made any changes to the xaml files - I get the exception as soon as I open a newly added xaml.

Any ideas? Thanks in advance
Andy