Giorgio,
I think the difference I am seeing is viewing the report from the Portal vs. viewing from the WRS system. I have one report deployed that has the Data View hidden from users, however I am having trouble duplicating. I was beginning to wonder if it was related to the Save button vs. Save As and replace existing.
There is some .jsp that you can modify to change whether this is checked by default.
/ SAS/SASWebReportStudio/4.2/Static/wars/
"toggleSidePaneFromViewMenu" function is available at: tiles-components/mainReportLevelMenus.jsp which might get you started.
NOTE - Document this change EXTREMELY well. When you are implementing future hotfixes/maintenance releases/versions - there is a possiblility that this file will get replaced.
Angela Hall
Zencos Consulting
http://www.zencos.com