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.

Not every time, but with about 50% chance sound played by mplayer 
interrupts for ~0.5 sec when I maximize some window (ex chromium browser).

Is this likely a bug in nvidia driver that it locks up the system when a 
lot of OpenGL operations are in progress? Or is this a necessary evil 
and has to be this way?

Yuri