Search dosen't work on Chinese Characters

I found the search function acts a very strange behavior in RC1. Almost all words can't be searched. Fox example, I search the word "注册", it results in error:

The following words in your search query were ignored: 册 注.
You must specify at least one word to search for. Each word must consist of at least 3 characters and must not contain more than 14 characters excluding wildcards.

Expecting somebody take a look in this problem. Thanks
You can try it on my test forum, I have just built the search index for it.
http://www.phpbbchina.com/phpbbpro