I've been having similar on-going problems. The only difference is that the problem is intermittent for me. Sometimes my program works fine, other times it throws the same Exception you described on first attempt to perform any administrative web service operation. I had wondered whether it was somehow connected to how previous sessions were terminated. In any case, I've not been able to figure this out either. I can't believe there is not already a solution to this or some configuration requirement, as I don't see how anyone would be able to use any web service calls.
Any advice would be appreciated.
Carlos S. Zamudio