In a freshly installed Kubuntu 8.04 RC, if the system language is an East Asian one, such as Simplified Chinese, which is chosen during system installation, then the default X input method should be "scim", not "scim-bridge" which is currently the default.
See this screenshot for illustration: http://tinyurl.com/5lcs7n
Also, if English is chosen to be the system language during system installation, and after the installation the user installs and adds an East Asian language (e.g. Chinese) from System Settings -> Regional & Language, then the default X input method (as in the screenshot) is still "XIM", not "scim". I recommend that as long as at least one East Asian language is added, the system automatically switches the default X input method (as seen in the screenshot) to "scim".
As a bonus, all the other options ("scim-bridge", "XIM", "Simple Composing Input Method") should better not be displayed because they're useless anyway.
Is this still an issue for you? What Ubuntu version do you use? Thank you for telling us!