MetadataException when using Entity Framework Entity Connection

This code:

using (EntityConnection conn = new EntityConnection("name=ELSCommonEntities"))
{
  conn.Open();
}

Gives me the following error:

Test method ELS.Service.Business.IntegrationTest.Base.ServiceBaseIntegrationTest.StartLoggingTestMethod threw exception:  System.Data.MetadataException: Unable to load the specified metadata resource..

With the following stack trace:

System.Data.Metadata.Edm.MetadataArtifactLoaderCompositeResource.LoadResources(String assemblyName, String resourceName, ICollection`1 uriRegistry, MetadataArtifactAssemblyResolver resolver)
System.Data.Metadata.Edm.MetadataArtifactLoaderCompositeResource.CreateResourceLoader(String path, ExtensionCheck extensionCheck, String validExtension, ICollection`1 uriRegistry, MetadataArtifactAssemblyResolver resolver)
System.Data.Metadata.Edm.MetadataArtifactLoader.Create(String path, ExtensionCheck extensionCheck, String validExtension, ICollection`1 uriRegistry, MetadataArtifactAssemblyResolver resolver)
System.Data.EntityClient.EntityConnection.SplitPaths(String paths)
System.Data.EntityClient.EntityConnection.GetMetadataWorkspace(Boolean initializeAllCollections)
System.Data.EntityClient.EntityConnection.InitializeMetadata(DbConnection newConnection, DbConnection originalConnection, Boolean closeOriginalConnectionOnFailure)
System.Data.EntityClient.EntityConnection.Open()
ELS.Service.Business.Base.ServiceBase.StartLogging(String userWindowsLogon) in C:\C-TOM\ELS-RELEASE1\ELS.Service.Business\Base\ServiceBase.cs: line 98
ELS.Service.Business.IntegrationTest.Base.ServiceBaseIntegrationTest.StartLoggingTestMethod() in C:\C-TOM\ELS-RELEASE1\ELS.Service.Business.IntegrationTest\Base\ServiceBaseIntegrationTest.cs: line 65

However, this code which uses the same connection string:

using (ELSCommonEntities db = new ELSCommonEntities())
{
    var res = from c in db.Logging
              select c;

    int i = res.Count();
}

Does not give an error.

The connection string is:

<add name="ELSCommonEntities" connectionString="metadata=res://*/Common.CommonModel.csdl|res://*/Common.CommonModel.ssdl|res://*/Common.CommonModel.msl;provider=System.Data.SqlClient;provider connection string=&quot;Data Source=localhost;Initial Catalog=els5_demo;Integrated Security=True;MultipleActiveResultSets=True&quot;" providerName="System.Data.EntityClient" />

I have also opened up the dll in reflector and the metadata looks ok.