Some users have reported that they could not access the corpora from their machine. I am not sure what is going on, but the problems may be related to firewalls. If your windows logon user name contains Chinese characters, Xaira also cannot work because it needs to access the temporary directory.
the BNC world edition is issued because some files in the BNC verson 1 are restricted to Europea or America. I think a similar approach can be taken for Chinese corpora - making resources for which copyright can be cleared publicly available.