i have same "clicking" noise in nulldc when i play mortal kombat gold !!
after setting buffer to 2048 or 4096 it becomes better but not enough.
then i tried the older 1.0 beta1 nulldc from 1.april and now its working nearly perfect under vista 32bit with creative x-fi soundcard !
maybe this will help you to correct in next 1.7 beta release
