I found that Versions 18.104.22.168 still has two problems with Korean Windows XP.
1. Calendar item is not saved. The only way to fix it was to change date/time description language from Korean to English through control panel. But this is not practical for Korean Windows XP, because that change incurrs many problems with other application softwares.
2. Even worse, whenever I try to type in the first letter for the name of the thought, PB just stops. To speak exactly, the input process for thought name freezes... I have to kill the process through Ctrl-Alt-Delete managing tool.
P.S. I guess the new 5.5 versions are not compatible with "Korean" Windows XP... Hence I went back to the previous version of PB, Ver 22.214.171.124.