Error CS0006 Metadata file System.Xml.dll could no

This had previously worked on the Win 7 (64) laptop. We have several other Enterprise Lic. and thay are working fine all connected to single SQL Server.
I have uninstalled and reinstalled several times with reboots in between and no luck.

Need help getting this support Laptop back up and running.

Thanks

Full error message below
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Standard Edition 5.9.0.0
InvalidOperationException - Unable to generate a temporary class (result=1).
error CS0006: Metadata file 'C:\Windows\assembly\GAC_MSIL\System.Xml\2.0.0.0__b77a5c561934e089\System.Xml.dll' could not be found

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 Devolutions.RemoteDesktopManager.Managers.SerializationManager.GetSerializer(Type type)
at Devolutions.RemoteDesktopManager.Managers.SerializationManager.SaveObjectToString(Object value)
at Devolutions.RemoteDesktopManager.Managers.SerializationManager.SaveObjectToFile(String fileName, Object value)
at Devolutions.RemoteDesktopManager.Managers.OptionManager.DoSaveOptionsObject(String fileName, String backupFileName, Object data)
at Devolutions.RemoteDesktopManager.Managers.OptionManager.SaveOptions()
at Devolutions.RemoteDesktopManager.Managers.OptionManager.DoLoadOption(Boolean checkAutoStartup)
at Devolutions.RemoteDesktopManager.Program.Main(String[] args)