PMDG 737 800 Sound Problems

I am having a bit of a strange problem with the sound on my PMDG 737 800.I just installed PMDG on a new system. The connector for my speakers work fine but when I plug my headset in the sound in my speakers goes off. Now I know this is supposed to happen so I changed the position of the jacks on the back of the system so that the sound will still be heard from the speakers and the headphones and mike set.This works fine with all aircraft with the exception of PMDG. If I load any other aircraft then I get sound in both but if I load PMDG I only get sound from my speakers or my Headset but not both.The strange thing is, The only sound I can not here is the engine sounds. I can get all the call out's "Bang angle, 80Kts and so on" from my speakers when the headset is connected but not the engines.Is there anyway I can resolve this issue.