Missing sound

[bucaneer]

Hi fellow simmers,

Have a bit of a problem with sound while flying around in FSX.

For some reason once a flight is underway my sound seems to go into 2.1 stereo mode, at least that's what it seems like.
Correct sound device is selected in the options set up GUI, and FSX music is playing nicely in 5.1 Surround as I make all other selections.
For some reason the minute I go into flight mode with any aircraft, the sound changes back to basic 2.1 with no surround sound evident.

Have tried deleting FSX cfg to rebuild a new file, but it did not work.

The sound card is a Creative Soundblaster XFI-5.1 Surround card and has the latest driver version installed and it is working just fine in every other program,
for instance iTunes, Cd playback and so on.

Stumped as to what to do.

Any ideas folks. Thanks.