The proxy type created in the method GenerateProxy() does not have its __objectFactory field set. This results in a reference null exception when the emitted constructor code is invoked.
Until the bug is resolved one can circumvent the problem by using a class derived from Spring.ServiceModel.ServiceExporter and overriding the GenerateProxy() method like so:
protected override void GenerateProxy()
Type proxyType = typeof(ServiceExporter).GetField("proxyType", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(this) as Type;
proxyType.GetField("__objectFactory", BindingFlags.NonPublic | BindingFlags.Static).SetValue(proxyType, objectFactory);