There are early reports via WebmasterWorld of fluctuations in the rankings at Yahoo Search.
The reports came over the weekend where some have seen large jumps or declines in rankings within Yahoo.
Yes, I had a drop from #7 to #18 for a 1 word search that had been stable for a while. No other changes seen on that, or any other sites though.
This may be a small update, since the last update was just a few weeks ago.
Forum discussion at WebmasterWorld .