The Top Ten Diaries is offline presently because the query (amongst a couple of others) was killing the system. It needs redesigning to be more MySQL friendly (which is bizarre, but MySQL really chugs on some queries on the entries tables now)
I think ADM jokingly said in one of his entries - maybe there are too many diaries on the system - in a way its true, the problem is that the entries table has become so huge that any query that joins to it really needs to be seriously optimized otherwise it goes nuts. Anyway, we're getting there
Steve