If I'm in a server and there is nobody else, sound effects play fine.  But when I'm on a server with other players, the sound that they make when playing I hear as odd pops and blips in the audio.  It's definitely the sound that is being generated by the other players fighting in the level.
I have attached my dxdiag report.  I have the latest sound and graphics drivers.  I have also tried lowering the hardware sound acceleration level from full acceleration in increments to no acceleration and the problem persists.

email support@instantaction.com

Just to say that I have the same problem.

Another one is if I activate jetpack after respawn I hear the jetting sound a lot louder(or skating sound, not sure which one it is), than if I activate it later.

I'm going to bump this and say I'm getting this issue too, using an X-Fi XtremeGamer, for what it's worth.

Edit: I reformatted and updated to the latest drivers, no change.

another bump.  i have a buddy who has this same issue from time to time.

I have all of the problems mentioned in this thread. A while ago I made my own thread about it but it didn't get a single reply.

i have an creative audigy2 zs, it seems that i have this problem too since i updated to the newest driver.

old one:
Creative Sound Blaster Audigy 1.04.0061
22. April 2006

new one:
Creative Sound Blaster Audigy 2.18.0001
17. Juli 2008

windows xp sp2