Vit --
In Project Server 2003, when you close a project, the system automatically
publishes your project using a Collaborate - Publish - Project Plan
operation. It does this without asking your permission, and does not even
tell you it is doing so. This is a change from the default behavior in
Project Server 2002. Alas, there is no way to change the way the software
works, so you will have to live with it. The only good thing about this
behavior is that the automatic publishing operation does not publish task
assignments, so at least your team members don't see their assignments until
you actually do a Collaborate - Publish - New and Changed Assignments
publishing operation.
If your team members are actually seeing their assignments even though you
did not publish the project, then go to Tools - Options - Collaborate and
deselect the options in the On Every Save, Publish... section at the very
bottom of the dialog. Hope this helps.