The system is Win7 64 bit.I am using an Audiophile 2496 soundcard. The MB audio is disabled in the BIOS.The system has been in daily use for more than two years.No software updates or additions have been done recently, except perhaps the uncontrollable MS Security Essentials updates.Perhaps someone knows what causes a recent problem and how to fix it.The Audiophile contains a DSP mixer chip. This computer is not used for recording, only for working on recordings. Normally I do not use the soundcard mixer, I set the I/O directly to the ADC in and DAC out.Last week a question arose about monitoring the input against existing tracks while recording an additional track. Under the Win7 driver, the Audiophile Control Panel is significantly different than my previous experience with it. I played with the settings to find how to set it up for monitoring the input + output. After I figured that out, I set it back to my normal.Everything works as before, so I think it is set as before. Actually, almost everything works as before.Frequently, the computer is on all day but not necessarily is use. If I expect to do something else for awhile, I select Sleep mode and it shuts down to no apparent activity except a blinking LED. This is never done on timer, only manually. It is simply a convenience: the machine is on and ready to use much faster this way than if starting from complete off. Sometimes it remains in sleep mode all night rather than being shut down.Until I played with the Audiophile Control Panel last week there was never any audio problem. Every since my Control Panel experiment, audio is missing when the computer is awakened from Sleep mode. Several media player programs simply do not respond when I try to play something. Cool Edit 2000 thinks it is running, the cursor advances and the VU meter display the level, but nothing gets out. The M-Audio Control Panel VU meters do not show any activity.A warm boot restores audio functioning. Since nothing else is required to get back to normal, I take this as evidence that my Audiophile Control Panel settings are as they should be, but that is only conjecture. Either there is still something I can't see in the settings or temporarily changing these settings forced something elsewhere to change, something that has not come back to where I want it.