In my opinion, the CE-Star 2.8 r3 was the most stable Chinese Traditional input application for O2 Atom with Windows mobile 6 and 6.1, because I also using this with my windows mobile 6.1 currently (stable also when I using windows mobile 6).
But unfortunately, I loss the link to download this, you may try to search this from the search engine at http://www.google.com
, sorry for inconvenient...
O2 XDA Atom
Expension Memory: Toshiba 2GB MiniSD
OS: Windows Mobile(R) 6.1 Professional by PDAVIET
(CE OS 5.2.20765) with PagePool 6MB