[Wine] Why flash in Firefox doesn't always show Chinese words?

[Yuri]

I run Firefox under wine with flash 10 installed.
This page: http://www.quickmandarin.com/chinesecharacter/
has a nice display of mandarin words, but very often it shows rectangles 
instead of words.
How can I figure out why words aren't shown? How can I know which fonts 
are used?

Virtually all other web sites with Chinese display correctly.

Yuri