Romout

Same for me - I had the problem that a callback method implementation was not able to re-invoke the server. Of course, I've tried it with ____ServiceBehavior____(ConcurrencyMode = ConcurrencyMode.Multiple, UseSynchronizationContext = false) - It took ages until I found Anon's post or better, Reddest's reply to it and realized that I did exactly the same mistake.