Apologies if this has already been posted but I did look through the news and couldn't find it.

It appears that its only been announced today -

J-pop diva Hamasaki Ayumi (30) had to undergo emergency surgery after she injured her hand in a fall on Christmas Eve. Her agency didn't reveal the extent of the injury but said she had surgery on Christmas Day. On doctor's orders, she has had to cancel a scheduled appearance on today's edition of the TV Asahi show "Music Station."

Source: http://www.japan-zone.com/news/2008/12/index.shtml

I've not been able to find anything futher out about it, this seems to be the only article at the moment. I hope she is alright, what a horrible way to spend Christmas