How did you host your WCF service? and Did you access your service from client application in another computer? What your meaning is that the error was throwed while accessing the service from the service hosted server? Could you paste the inner detailed error information? you could enable WCF tracing on the server and client side to see the inner detailed executed information.

#enable WCF tracing.
http://blogs.msdn.com/b/madhuponduru/archive/2006/05/18/601458.aspx