Windows 95 Loses Sound

I have 24 Windows 95 machines all with brand new Sound Blaster PCI16 cards. About 8 of the 24 machines have intermittent sound. I have installed the latest version of the drivers. Does anybody have any suggestions. It seems that in the AM all sound works great then as the day progresses we lose sound sometimes rebooting will bring the sound back sometimes it will not but after the computer sits all night sound always comes back – Strange!