I am facing the same problem. I have ensured that I have followed all the steps given in the installation mannual. This clearly indicates there is some thing wrong with the workbench installble (trail version). I do not know is it by design (intentionally done by Adobe it self). If it is so, its shame on Adobe.
The trial version is the same as the production version - so the instability is not intentional. Can you hit the server from another client running Workbench?