"Services -> Intrusion Detection -> Administration -> Schedule
After you enter the first schdule here, the tab breaks and can no longer be used to add or edit schdules. You can find the first and only schedule you created here under System -> Settings -> Cron but the actual Schedule tab for the Intrusion Detection function has stopped working and can not be used anymore.
I have this same problem. It immediatly pops up with a new schedule creation. When clicking Cancel, it take you out of the schedule tab.
Well, i don't get a "new schedule creation". It opens the current schedule in Edit mode. Looks very much by design.