I had my World book working fine then encountered a similar problem to this and discovered that when i plugged the Western Digital directly into my Mac ethernet port the drives and bonjour related instances all reappeared, thus implying the problem was with my router.
When i went into my router settings I realised I had recently turned off an option to “Allow multicast from Broadband Network”, on reactivating this (or factory restore the router if necessary) the drives reappeared on my mac, the bonjour instance to connect to the drive reappeared in Safari, and my itunes shared server reappeared in itunes. It appears in order for the drives etc to appear on the mac they are effectively “broadcast” so enabling multicast from Broadband Network appears to be the answer in my case at least.
At best I would suggest restoring the router to its factory settings if you find when connecting the drive directly to your ethernet port that the drives and so forth reappear. Hope that helps.
