Wordpress problem with Chinese characters

I have a problem with my wordpress. I've tweaked certain files to make Chinese characters display, and whilst Chinese characters are now displaying, there is a problem with formatting posts. No matter how long the post is, when it comes to saving as a draft or publishing the post, only two lines of characters remain. I need this resolved so that posts format as normal, and Chinese characters can still be displayed within the posts, categories, tags, post titles etc.