It can happen that there is a corrupt/faulty document in the busytime/clubusy database. Today, you have to recreate the whole database to fix this issue. It would be nice if there is a command to just recreate this single document. "tell sched validate" or "tell rnrmgr validate" is not helping in the most cases!
Recreate busytime/clubusy: http://www-01.ibm.com/support/docview.wss?rs=899&uid=swg21086471