Plugging USB sound card prevents Windows Screen saver from running

Question

I'm developing an embedded Windows based device with some extra hardware (an information kiosk). I need second sound card in the device so I use USB Device like this

but when I plug it in it prevents Windows screen saver from starting. When I pull it out the screensaver works again.

I use Windows 7 pro 64-bit. With default driver from Microsoft (version 6.1.7601.17514). There are no "power management" options on device's proporties dialog :(

Thanks in advance for Your help.