XElement over WCF - strange error

Question

One of my WCF service is returning a XElement object. Visual Studio, the client web app, is keeping showing this message

Cannot convert source type 'System.Xml.Linq.XElement[Service.Contracts, Version=1.0.0.0, Culture=neutral]' to target type 'System.Xml.Linq.XElemnet[System.Xml.Linq, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]'

above this piece of code

XElement xml = xmlService.Get();

Both apps are on the same computer. The project compiles just fine,no error is shown,but it's anoying. What could be the problem ?

BTW Should I rather return a string and the parse it ?

Answer 1

After computer restart, it works fine again.