Thanks for the suggestions, Stéphane: yes ordinary exceptions where thrown from a file in Nicolas: I can now reproduce the problem in a workspace as well The following code, evaluated from a workspace hangs Pharo (1.3 One-Click): ZnServer removeFromSystem. Gofer new squeaksource: 'ZincHTTPComponents'; package: 'Zinc-HTTP'; load. (Smalltalk at: #ZnServer) startDefaultOn: 1701. Apparently, just loading the code using gofer and starting the server is not enough to cause problems; there has to be a significant change, hence the removeFromSystem, before trouble begins. Since the progress bar says 'Initializing..' could there be something wrong with ZnServer class>>#initialize ? It looks harmless to me. Could someone please confirm this crash/hang ? This reminds me of the other problem that we had with the units tests, where the trait compilation tests before a Zn test involving a server caused problems. I still don't see a relations, but there has to be something very strange going on here. Sven