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There is a very good research site about this topic entitled :Empirical Analysis of Internet Filtering in China [cyber.law.harvard.edu]. This site details a lot of the reasons a site may be banned in China, and may answer some of your questions...but not how to get un-banned.They also have Real-Time Testing of Internet Filtering in China [cyber.law.harvard.edu] where you can ask them to check whether your site is being filtered. I haven't tried this as none of my Chinese sites have been banned in China, but this might be something that interests you.
Maybe some of our members from China could comment further on this.