distorted Sound in host when VB is launched

[Froeschlein]

Hey there,

I just installed Win7RC64 on my host machine and set up a VBox with Ubuntu 9.04 as guest.
As soon as I start the VB, the sound of the host gets noisy and distorted... like there is way to much gain.
Turning of the VB doesn't help, I always have to reset the sound driver settings of the host (creative soundblaster x-fi-gamer-somthing)...
Changing the VBs audio card to SB16 would result in no sound in the guest and normal sound in the host.
Just the AC 97 setting shoots the hosts sounddriver (as it seems...)

I didn't find much about this topic in the net so maybe you guys could help me out?

Thanks in advance!

Chris

P.S.: I'm no native speaker so please don't blame me for my english :-/

[Froeschlein]

Anyone?