Sound freezes system (Via Vinyl AC'97)

Here's a problem that's driving me nuts with an otherwise excellent OS.

I'm running Win7 (RC1, 32 bit) on a Fujitsu-Siemens Amilo A7640 notebook (1GB RAM, Mobile AMD Sempron 3000+), which uses VIA Vinyl AC'97 (VIA VT1612A AC97) to playback sound.

The system has a habit of freezing when playing sound. It doesn't seem to matter what program is playing the sound, as I have had my instant messenger, email notifier and browser (online videos) all hang the system. So, it is not program related.

When the system hangs, the screen freezes, the mouse pointer doesn't move and the keyboard is unresponsive (CRTL+ALT+DEL does nothing). The only way to deal with it is to press the power button for a few seconds to switch off the computer.

But this doesn't happen every time I play sound. I can for instance watch a number of online videos just fine and then have everything freeze when I start the next one. The problem is also not related to any particular sound or video since after a reboot I can watch a video that crashed the system just fine.

Actually, I am not 100% sure but it seems to me that what causes the freezing is the start of sound playback. If the playback starts ok, I will be able to go through the whole audio/video without problem.

I have tried a number of things to fix this. The default audio driver installed by Win7 already had the freezing problem, and the one I got from the Fujitsu-Siemens website (marked compatible only for XP) did the same. I tried the latest driver from Via (Vista compatible), but it didn't solve the problem. After installing it I noticed that Windows Update now had an optional sound driver update which I installed, but it didn't help either. I have also tried some Realtek drivers but no help there.

That is not to say that all drivers have been equal. While changing drivers hasn't solved the freezing problem, the driver originally installed by the OS as well as the driver from the Fujitsu-Siemens website caused the sound to crack and pop during playback, rendering them useless. The latest Via driver fixed this, and the subsequent Win7 driver update hasn't returned the problem. So the audio plays well now, unless it freezes the system.

I have tried fiddling with the Speaker Properties settings. Changing S/PDIF, Default Format and the settings of the Exclusive Mode appear to have no impact on the problem. However, I don't fully understand what these settings do, so if someone can suggest an optimal combination to try out, please do so.

There is one more symptom -- the sound sometimes disappears. For instance now that I press "Test" on the 'Advanced' page of the Speaker Properties window, I can hear the first note or two, and after that silence. Just a moment ago, I could hear the whole sound test. Sometimes when I start playing an online video, there is no sound. After I reload the page and try again, the sound works ok.

If I remove all drivers, therefore getting rid of all sound, the system doesn't seem to crash.

Also, I am not sure if this is related, but just in case it might be: the only other problem I have with the OS is with the sleep mode. If I close down all the programs and then put the computer to sleep, everything works fine. However, if I have any programs running, the computer goes to sleep ok but when waking up simply gives me a black screen with lots of hard drive activity. The only way to deal with this is to shut down the computer by pressing the power button for a few seconds.