I just upgraded my rig last night from gigabyte 5850's x2 and the on board audio to an evga 670 4gb and a creative sound blaster fatality soundcard
For about 3 hours it was all running fantastically. Bf3 was running like a charm and I definitely noticed a difference in sound quality but then suddenly with no apparent reason I lost all sound, in game, in itunes, even the windows start up sound.
I tried switching back to the on board audio to see if my speakers had gotten messed up somehow but even then still no sound. I plugged my headphones into the front port with the same result
Before you ask yes I updated both the graphics card and sound card drivers. I didn't, however, update my mobo drivers because I'm not sure which ones TO update.
Could the mobo drivers be the problem? and if so why was it working perfectly for a few hours?
Sudden failure while in use would seem to indicate some sort of component failure.
There's no harm in trying new drivers and such, (just create a restore point first) but I doubt your drivers suddenly became incompatible in the middle of playing a video game.
I suppose it's possible that the motherboard "learned" to route audio through the card and didn't "relearn" audio out the original ports if/when the audio card failed. (A CMOS reset would probably fix that scenario)
However, my best guess is a problem with the motherboard.
If the motherboard did fail, I would suspect that a power supply problem may have caused the MB failure.
My suspicion stems from the assumption that routing audio through a sound card doesn't particularly "stress" a motherboard and thus shouldn't cause it to fail.
Connecting two GPU's to a power supply can, however, stress a power supply and some power supplies do very bad things under stress. Ripple and noise can get introduced to your components and then they can fail.
If you can't find a reset button on the motherboard or the jumper, just pull the power cord from your power supply, remove the watch battery and leave it out for a bit, (Might as well remove the suspect audio card while you wait) then reinstall the battery and power cable.
When you turn your computer on, the motherboard should now be at all default settings.
In playback devices set your realtek speakers as default, it should have a green tick. Use the speaker outputs at the back of your computer to rule out if the front panel audio out hasnt been wired to the sound card instead.
Not sure whether you tried onboard sound after installing sound card though check your bios and make sure by installing the sound card hasn’t disabled onboard sound automatically.