Sound on the system briefly interrupts when kde4 switches windows with nvidia card

[Yuri]

I have kde4 on 8.2 with translucency windows effect enabled and nvidia 
graphics driver.
Every time I switch an active window or maximize some window, sound 
played by mplayer interrupts for ~0.5 sec. Very annoying effect. Problem 
disappears when windows effects in kde4 are turned off.
Is this likely a bug in nvidia driver that it locks up the system when a 
lot of OpenGL operations are in progress? Or what might be a problem?

Yuri