Sound cuts out in FS9

Thanks in advance - all sound cuts out at random times when I'm flying. It doesn't seem to be triggered by anything specific (such as changing views), and sound returns if I hit 'Q' (to turn sound off) and then 'Q' again to turn sound back on. I've set dxdiag sound to 'basic', and I've reloaded all drivers (except for my Sidewinder Pro - the driver that came with XP seems to be the most current). Any suggestions? Same thing happened with 2002. P4 2.4GeForce 4200 128Realtek onboard audioSidewinder ProXP Pro.