I cannot replicate this, and nobody else has reported it.
GSX never tries to use the sound card directly ( it uses OpenAL ), and it doesn't use any of the simulator own sound services so, nothing in the sim version should change how GSX use sound, since it was never related to the sim itself.
Could be you changed something in the simulator affinity settings, or you have a 3rd party utility that might have changed that without you knowing it ? The simulator itself stealing too many cpu cycles for itself is the only thing I can think of that might cause GSX to get less attention from the OS, possibly reducing perfomances. Usually the OS itself does the better job at handling this, so it's best not to touch these settings.