From what I remember the logout issue is caused by proxies caches and the fact that smalltalk hub does not set any headers that prevent/invalidate caching.
We are having this problem all the time on our university network. To make it worse sometimes after I log out I get the home page of the previous logged in user that accessed smalltalk hub.��
If the underlying cause is caching then smalltalk hub could add some headers to invalidate it. We really only get these kinds of problems on smalltalk hub.
Cheers,