Been a Issue with me lately, Im not sure what is causing it.

So, For Examples:

When I goto Play DCS:
I Boot Teamspeak, login, Say Hello.
Boot DCS, No Sound, Goto MP, No Sound, Get in flight, No Sound.
Close DCS, Close TeamSpeak, Open DCS MP, Login, Get in Flight, Minimize DCS, and Goto TS3 and login. Sound Works.

BF3:
Open BattleLog, Create Group/Join Voice Chat, Say Hello, Join a Server, No Sound in BF3, Close BF3.
Close/Leave Voice Chat, Join Server, Re-Join Chat, Everything Works.

iRacing:
Join a Race, Press PTT, no one hears me, quit, check Default Communications device, working fine, go back into race, tinker with Audio Device Settings, Eventually get it to work, and have to repeat for the next race.

YouTube:
Search for a Artist, Open Video A, Open Video B, Open Video C.
Video A Has Sound, when it finishes, goto Video B, No Sound, Video C, no sound, but if I Close off Video 1 and Refresh the page on Video B or C I Have sound.

Another Situation, Open Video Start Watching it, Another Application Makes Noise/notification, I Lose Sound on Video, Have to Close Application, refresh page, to get sound back on Video.

Watching Videos in VLC/Windows Media Player.
Every now and then the video has no sound, I have to close it and re-open it.

It seems like something is limiting to sound driver to one thing or not letting it switch between more than one application?

I've checked Volume Levels Hundreds of times.

Originally thought TS3 was muting audio, but It's happening when using other applications as well.

Thought it was the Sound Card powering off and On, nope.

I'm Thinkin' it's a Driver Issue. I think I Updated the Driver through Creative a few months back.
Or a Windows Update.

Sounds like you've done all the obvious things with audio device settings, so probably not that. I seem to remember a laptop that had a similar issue that was solved by changing the power settings, I realise that you're not on a laptop, but maybe one or more of your power settings(Pci maybe?) have been changed with an update? Worth a try before rolling back the drivers perhaps.
Boko.

it's not turning off,

Forgot to mention, the whole time I'm booting DCS With no sound, Im still talking to and hearing everyone on TS3,

It's like Windows is having an issue with letting more than one Program have access to the Audio Stack.

Can you post details about your Windows control panel Advanced sound settings?

Check the Windows Sound Playback settings for your speakers/headphone device, there is a setting to allow applications to take control of the playback device, you should be able to turn that off.

weird that box is checked on my brother's PC and he has no issues..... and he's running an nearly Identical setup as mine.

NSA is intercepting your audio, but not your brother's...

I unchecked the option,

and abused Youtube last night, I had like 25 videos playing out of 60 open.

The audio did start to distort after 4 or 5 windows,,,Upiong my Sample Rate back to 192KHz fixed a few other things, dunno why it was put down to 44.1KHz, I've always Had it at 192KHz.

This weekend I'll prolly go through the Hardware Settings for the X-Fi and triple check everything, I think when Creative's software updated it reset everything to defaults maybe?.

That doesn't make sense... Most audio isn't recorded for 192Khz playback. Most games and mp3s are 44.1 or 48. Strange issue...

I use Studio Equipment that runs 192KHz.

Yes, I get that. What I meant to say is that most music you purchase or rip off CDs isn't that high of quality. Most of my MP3s and CD rips are at 44.1 @ 256 or 128 kbps.

Im actually still having this issue,

boot TS3, I get no audio in DayZ,
Boot DayZ, I get a Prompt saying there's no playback device when I Open TS3.
Have TS3, or any game open, Alt Tab, WMP Wont open video, VLC Opens with no sound.

I'll have to double check stuff when I open the case for a routine cleaning.

If I were you, I'd take the card out. Remove all Creative drivers using the uninstallers then use Driver Fusion to do the rest in Safe mode.

It's been fine for 2 years, funny this started after I let windows catch up on updates.

I betcha those 2 updates I keep unchecking and choosing to "HIDE" snuck back into the list.

Might also be something with the adjustments MS made to Power Profiles, as it seems to be fixed by rebooting. I also Disabled my AMD Outputs (for the screens, since they arent being used) and my ASIO/Studio Gear Devices (since I'm not using them at the moment, if the problem persists I'll know it's not them).

I will test more, but Right now I'm assuming it's a Windows Issue with either an Application Not letting go of the Audio Stack or a profile issue, since Windows Moved to the Software Audio Stack, this type of stuff isnt supposed to happen.