IMFTest does not work the majority of the time on RedHat AS 4. You are unable to activate the language input selection, when you click on the shift and space key combination. However, this works fine using any other native applications, such as gedit. This was tested on locales ja_JP and zh_TW.
Further testings show that using "Ctrl-space" can switch to input japanese on Redhat AS 4. The only thing broken here is "Shift-space" no longer works for all legacy XIM clients. This issue has already logged as a openi18n IIIMF bug (http://www.openi18n.org/cgi-bin/bugzilla/show_bug.cgi?id=80).