custom dates not showing up in iCloud on MacBook

Events with custom dates (e.g., 3rd Thursday of the month) have stopped showing up in my Mac iCloud calendar. They still show up in iCal, and on my iPhone and iPad. They also showed up in all previous months in iCloud, but for some reason they stopped and none have appeared in February, 2013. I checked, and all the custom dates have no specified end date--and anyway, they continue to appear in iCal, iPhone, and iPad. I can't figure out how-come?