Hello!
Thanks for all your answers. @Vijay your answer was particularly useful because Esposito's was what I was looking for. After tweaking a beat with the override of the two methods I came to the conclusion that, yes, I can load a previously saved state for a page from another session BUT there's a couple of strange things happening:
1) First method firing is SavePageStateToPersistenceMedium -> I managed to get this one by coding if (!Page.IsPostBack) LoadPageStateFromPersistenceMedium.
2) Despite my previous code, the viewstate is only loaded after I postback the page to server (meaning that, hadn't I prevent the Save I would never get the saved state).
Dino Esposito's article lead me to this one in CodeProject: http://www.codeproject.com/KB/applications/persistentstatepage.aspx which, I think, is what I need but somehow it's not working at all, got to make further investigation.
Anyway, thanks again for all your answers.
Regards
Frank