After a short performance of just 30 minutes, Namie Amuro stopped and canceled her second concert at Yokohama Arena (November 6th) from the nationwide tour “namie amuro LIVE STYLE 2011” . According to Avex this happened because Amuro accused throat discomfort; Amuro came out and apologised after.
In a tweet posted by avex Amuro said that: “I am really sorry. My health is good, but I have a bad condition of the throat, my voice didn't come out right and I wasn't able to sing at a high place. Because I want to show you all a performence at 100%, please give me another chance."
Afterwards, in an announcement made by Avex, it was said that Amuro has been diagnosed by a physician with acute upper respiratory inflammation.
The concert has been rescheduled for December 27th.
Source: avex, avexnews tweeter
(My translation of the tweet is approximate)