Raven.Server.exe exception

I've never used RavenDb it looks interesting but I'm falling at the first hurdle. I've downloaded, unzipped and I run C:\RavenDB\Server\Raven.Server.exe and it flashes up and disappears.

I tried running from a dos prompt and I got this exception:

C:\RavenDB\Server>Raven.Server.exe
System.Reflection.ReflectionTypeLoadException: Unable to load one or more of the
 requested types. Retrieve the LoaderExceptions property for more information.
   at System.Reflection.RuntimeModule.GetTypes(RuntimeModule module)
   at System.Reflection.Assembly.GetTypes()
   at System.ComponentModel.Composition.Hosting.AssemblyCatalog.get_InnerCatalog
()
   at System.ComponentModel.Composition.Hosting.AssemblyCatalog.GetExports(Impor
tDefinition definition)
   at System.ComponentModel.Composition.Hosting.AggregateCatalog.GetExports(Impo
rtDefinition definition)
   at System.ComponentModel.Composition.Hosting.CatalogExportProvider.GetExports
Core(ImportDefinition definition, AtomicComposition atomicComposition)
   at System.ComponentModel.Composition.Hosting.ExportProvider.GetExports(Import
Definition definition, AtomicComposition atomicComposition)
   at System.ComponentModel.Composition.Hosting.AggregateExportProvider.GetExpor
tsCore(ImportDefinition definition, AtomicComposition atomicComposition)
   at System.ComponentModel.Composition.Hosting.ExportProvider.TryGetExportsCore
(ImportDefinition definition, AtomicComposition atomicComposition, IEnumerable`1
& exports)
   at System.ComponentModel.Composition.Hosting.CompositionContainer.GetExportsC
ore(ImportDefinition definition, AtomicComposition atomicComposition)
   at System.ComponentModel.Composition.Hosting.ExportProvider.GetExports(Import
Definition definition, AtomicComposition atomicComposition)
   at System.ComponentModel.Composition.Hosting.ImportEngine.TryGetExports(Expor
tProvider provider, ComposablePart part, ImportDefinition definition开发者_如何转开发, AtomicComp
osition atomicComposition)
   at System.ComponentModel.Composition.Hosting.ImportEngine.TrySatisfyImportSub
set(PartManager partManager, IEnumerable`1 imports, AtomicComposition atomicComp
osition)
   at System.ComponentModel.Composition.Hosting.ImportEngine.TrySatisfyImportsSt
ateMachine(PartManager partManager, ComposablePart part)
   at System.ComponentModel.Composition.Hosting.ImportEngine.TrySatisfyImports(P
artManager partManager, ComposablePart part, Boolean shouldTrackImports)
   at System.ComponentModel.Composition.Hosting.ImportEngine.SatisfyImportsOnce(
ComposablePart part)
   at System.ComponentModel.Composition.AttributedModelServices.SatisfyImportsOn
ce(ICompositionService compositionService, Object attributedPart)
   at Raven.Database.DocumentDatabase..ctor(InMemoryRavenConfiguration configura
tion)
   at Raven.Server.RavenDbServer..ctor(RavenConfiguration settings)
   at Raven.Server.Program.RunServer(RavenConfiguration ravenConfiguration)
   at Raven.Server.Program.RunInDebugMode(Nullable`1 anonymousUserAccessMode, Ra
venConfiguration ravenConfiguration)
   at Raven.Server.Program.InteractiveRun(String[] args)
   at Raven.Server.Program.Main(String[] args)
- - - -
System.TypeLoadException: Method 'WriteJson' in type 'JsonToJsonConverter' from
assembly 'Raven.Http, Version=1.0.0.0, Culture=neutral, PublicKeyToken=37f41c7f9
9471593' does not have an implementation.

C:\RavenDB\Server>

I'm a total nub when it comes to this software. Any ideas ?

Thanks

It seems to be an issue with version 206 I've gone back to 193 and it works fine.