When trying to debug a WCF ( windows communication foundation) .NET 3.5 framework library, you might encounter a problem where Visual Studio (VS 2008) refuses to run or debug the WCF web service.
The error you get from the WCF test client when trying to debug the WCF service is this – "WCF Test Client: Unrecognized option ‘targetclientversion’ specified"
1) Close Visual Studio
2) Install the latest version of Windows SDK for Windows Server 2008 and .NET Framework 3.5
3) open Visual Studio again
This solved the problem for me.