Some Chinese words do not being supported

Hi,I'm a Chinese and use the Big5 code(Traditional Chinese).
Today when I tried to add a poll option I found that some Chinese words(such as "will" in Chinese) can not be displayed as usual as others,the unsupported word became a "?"
What can I do to fix this problem?

Hi,me again :o
I have another question.
In Admin Center I see $key in poll_view
and $key_val in poll_result
I tried to delete the words _val and it's still fine,
what is the different between the two VAR?

good, so write it into english

Sorry,my site is in Chinese.