How can I set the locale of gtk?

[Carfield Yim <carfield desktop carfield com hk>]

when I run many application these day, they complain that C haven't have
that locale:

Gdk-WARNING **: locale not supported by C library

and when I use command "printenv | grep "LC" ", I got the following:

[carfield desktop carfield]$ printenv | grep "LC"
LC_MESSAGES="en_US"
LC_TIME="en_US"
LC_NUMERIC="en_US"
LC_CTYPE="en_US"
LC_MONETARY="en_US"
LC_COLLATE="en_US"

anything wrong?