I'm also having the same problem. I thought of a couple of reasons why but nothing has worked so far. I tried:
1) Changing the language setting to Simplified Chinese while editing.
2) Installing a Chinese language font.
The problem is that the editable content areas and text fields don't recognize Chinese characters. Using the language pack merely edits the uneditable sections.
Can anyone think of a reason why Moodle wouldn't support non-latinized characters in their content fields?