Why input Chinese via Trackpad works in Skype but not in Firefox ?

When running Skype version 5.8.0.1027 and Firefox version 14.0.1 in parallel in the iMac, I can input Chinese via handwriting on the Apple Trackpad within the Skype program but NOT within the Firefox program. When trying to activate the Chinese handwriting input within Firefox, only trigger the mouse arrow hide or unhide. It has worked before in the earlier version of Firefox. The same problem happens when trying to input Chinese in my Word program (Mac version). Can anyone help to solve this problem ?