Thanks for your reply, very helpful. Your answer seems to match the situation but not 100%. What happened is, I tried to disable regular users from scheduling jobs but not for the Administrator or Administrators user group, of course. The administrators were still part of the BO but not able to schedule, even though they had a "Full Control" access.
What would you do in such a situation, Amit?
I have unticked "Inherit From Parent Folder" and "Inherit From Parent Group" on the user security for Web Intelligence. That fixed the access but I don't if it's the best way.