Mac OS X 10.6.8, Mac Pro 8x2.26, internal soundcard's linear output used.
There are two user accounts in the OS. If one user opens any browser (safari and opera tested) and loads any page with sounds (e. g. youtube) and plays sound and switch to other user's account, then there won't any sound from audiocard, even system's.
If switch back to first user, sound appears for a moment while switching.
If stop sound playback in first user's account, second user will be able to play sounds.
Also this problem appears for non-web applications, e. g. VLC, but not always.
P. S. There is also PCIe soundcard installed in the system. It hasn't any problems.
P. P. S. Sorry for my barely understandable English.
There are two user accounts in the OS. If one user opens any browser (safari and opera tested) and loads any page with sounds (e. g. youtube) and plays sound and switch to other user's account, then there won't any sound from audiocard, even system's.
If switch back to first user, sound appears for a moment while switching.
If stop sound playback in first user's account, second user will be able to play sounds.
Also this problem appears for non-web applications, e. g. VLC, but not always.
P. S. There is also PCIe soundcard installed in the system. It hasn't any problems.
P. P. S. Sorry for my barely understandable English.