Only default font in app code, while test program runs fine on system

Dear all,


I have a strange problem: Running standalone GD library test programs on 
my system, I get beautiful results -- while inside a larger app using 
the GD library, everytime the same (default-?)font (something sans 
serif) is displayed, which does not support Chinese.

Applying gdFontCacheSetup() inside seemingly did not do the trick... :-(

My guess is that the environment inside the app must be some way 
different -- but how??

Does anybody know of variables internal or external to the GD library 
which might block choosing fonts?

Has anybody a hint where to begin with debugging?


Thank you a lot in advance,

                 Nick