Looks like that “inexplicable drop” in Nickelodeon ratings from September that Viacom CEO Philippe Dauman noted in a November 10 conference call with analysts still bedevils the children’s network. Its full-day total audience was down 16.7% in the week of November 20. That gave Disney Channel its first victory over Nickelodeon since August 2007, when Disney introduced High School Musical 2. Nick’s audience of kids 11 and under was off 11% in September vs the same month last year, -17% in October, and -19% for the first three weeks of November. The reports worried Miller Tabak analyst David Joyce enough for him to downgrade Viacom to “neutral” from “buy.” He notes that “advertisers are going to want to pay for the lower Nielsen ratings, which could be resulting in make-goods … that could pressure ad revenue” in the current quarter.

It’s curious, though: When Dauman spoke to analysts early this month, he made it sound like the trouble at Nick was history: He called it “a short-term phenomenon,” adding that “I always believe in looking forward, so we’ll go through that blip, it’s not material to overall company and we will move on.” He also put the blame on Nielsen’s measurements — not Nick’s programming — noting that “independent set-top box data … shows meaningfully different viewership trends.” Nielsen has a different view. It says that its ”review process confirms that our measurement methodology, operations and related reporting processes are working as expected.” The Media Rating Council is looking at the matter and will present its conclusions to the companies next month.