I have a Lenovo running Win7-x64 (SP1), and after I put my laptop to sleep or hibernate, the computer won't play any sound after I wake it. The really strange part is that if I put the computer back to sleep/hibernate, it will play the sound when I wake it. (And it stops playing sound when I put the computer back to sleep/hibernate again). Rebooting the computer will also fix the problem. I have the latest windows updates and drivers.
There is a similar problem posted here, but there are no answers.