You might want to check on a Windows forum since it is a problem you are experiencing with Windows, not OSx, and your headset. Another place to check would be with your headset manufacturer's site and their support pages to see what they say about their headset and Windows 7 64 bit. When you go to these other forums be sure to tell them the name and model of the headset. Also, if the headset requires drivers, make sure you have downloaded and installed the correct Windows 7 64 bit drivers.
Thanks for your reply. The issue is with Windows, but it appears to be due to OSx drivers from bootcamp, that does not detect both input and output from the headphone jack. There are no drivers required, I have used this headset on various other Win7 x64 machines.
As above, it works fine in OSx, it is just that bootcamp drivers for the soundcard do not include that the hardware on my MBA allows both input and output from the same jack. Ms dont supply drivers for Bootcamp.