Do You use Your GTX760 to output audio through HDMI? Or You use integrated MB audio? If integrated don't forget to update Realtek® ALC889 driver also, from MSI site. Also get latest DX version.
Btw witch slot Your VGA inserted in? Closest to CPU? What is Your CPU/RAM? Win version?
One thing You can try is in playback device properties, advanced>default format, try to change it.