I am embarrassed to ask, because I had found the solution, and now cannot recall.
The messages box does not work in Web apps IDE so it is necessary to use the Windows equivalent of the Mac Console that tracks all messages for that app. In particular all System.Debuglog. I just wasted quite a while in Event Viewer and it is nothing like what I recall.
I remember downloading a program from Msdn but cannot find it back or remember what it was. Anybody can help ? TIA.