Cannot start mp "Class not registered" (1 Viewer)

[mrgnome]

TV-Server Version: ?
MediaPortal Version: 1.0 RC2
MediaPortal Skin: Default
Windows Version: XP pro
CPU Type: Core 2 duo
HDD: 250g sata
Memory: 2gig ddr2
Motherboard: gigabyte
Video Card: radeon 3850
Video Card Driver: catalyst 8.6
Sound Card: Internal Intel

I cannot start mp due to the following error, as soon as i click ok after the config screen:


System.InvalidOperationException: Unable to generate a temporary class (result=1).
error CS0007: Unexpected common language runtime initialization error -- 'Class not registered '

at System.Xml.Serialization.Compiler.Compile(Assembly parent, String ns, XmlSerializerCompilerParameters xmlParameters, Evidence evidence)
at System.Xml.Serialization.TempAssembly.GenerateAssembly(XmlMapping[] xmlMappings, Type[] types, String defaultNamespace, Evidence evidence, XmlSerializerCompilerParameters parameters, Assembly assembly, Hashtable assemblies)
at System.Xml.Serialization.TempAssembly..ctor(XmlMapping[] xmlMappings, Type[] types, String defaultNamespace, String location, Evidence evidence)
at System.Xml.Serialization.XmlSerializer.GenerateTempAssembly(XmlMapping xmlMapping, Type type, String defaultNamespace)
at System.Xml.Serialization.XmlSerializer..ctor(Type type, String defaultNamespace)
at System.Xml.Serialization.XmlSerializer..ctor(Type type)
at MediaPortal.Player.DSP.Settings.SaveSettings()
at MediaPortal.Configuration.Sections.MusicDSP.SaveSettings()
at MediaPortal.Configuration.SettingsForm.SaveSectionSettings(TreeNode currentNode)
at MediaPortal.Configuration.SettingsForm.SaveAllSettings()
at MediaPortal.Configuration.SettingsForm.applyButton_Click(Object sender, EventArgs e)
at MediaPortal.Configuration.SettingsForm.okButton_Click(Object sender, EventArgs e)
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)


I have tried reinstalling.
What can this be?