Solution
This is because Windows VISTA 64bit has some trouble allowing 32bit applications to output S/PDIF raw data to the audio playback device by using the WaveCyclic miniport driver.
To fix this problem, please kindly refer to the link to obtain the related patch file:
http://dlsvr01.asus.com/pub/ASUS/Audio_Card/Utilities/hotfix_KB936225_x64.zip