Hy!
I only have sound for 1 application at a time. if i listening music with audacious then nothing more sound can be heard. Like youtube or mplayer. I uing suse 11.0, and i have realtech alc 888 sound card.
Check your multimedia applications, and point them to use the “alsa” api as their input module, and not oss nor pulse.
I’ve also seen this problem, in some machines it exists but not every where. you may try by sound-card selection. My observation says it probably depends on the sound-driver and soud -card.