Anderton
Save a copy of the AUD.INI file, then delete it. SONAR will build new entries based on what you're using now. If anything goes wrong, which is extremely unlikely, you'll still have the old one for backup.

Cactus Music
As I said in post #18. I always have disabled on board audio. This good advice was given to me a long time ago on this forum. 
It has always worked for my system. Some systems and on board audio can co exist with ASIO but often there is a the issues as the OP described. So that is always my first recommendation. 
 
And I see no issue with using my "pro studio" playback system for everything. 
I turn most Windows sounds off or at least turn them down in the audio control panel so they don't scare the carp out of me. 
 
I like to listen to finished albums either in Win Amp as an MP# or even play back the CD I just burned in WMP. And I can keep Sonar open and swicth between all of these apps no problem. 
 
BUT!  one disclaimer and it might be the big one. I only work in 44.1. 
I cannot vouch if switching apps works if Sonar is 48 or 96 and Win Amp is trying to play a 44.1 file. 
I seem to remember back when I was using 48 that playing a 44.1 in WMP and on return to Sonar, that Sonar would get messed up and play the song a whole step low. 
 
But anyhow it only takes a minute to disable your on board and see what happens. 
And now we are told to also check for HDMI audio which is messing up a lot of systems lately. 
 
 

Anderton

Etostone
Btw, you never told me which is your Os ? win 7 or win 8 ?

 
I'm using Windows 7. Maybe that's part of it...I haven't used Windows 8.1 because of all the stories I've heard about driver problems with a variety of hardware devices (not just interfaces, printers etc.).
 

I am working fine with the new Asio drivers from this Australian programmer. He did a great job , and gives Tascam much further options ! Yes you should try it really. It has a total free to test drivers. It gives also the possibility to change the audio stereo from left to right channels inside the software , to have only one or two mono outputs very useful for testing your mix before radio mono conversion , giving each program different configuration and to save the profiles and many more.

 
Well, I prefer using ASIO drivers so I'm not interested in checking out a non-ASIO solution (Paul P is right, it's a wrapper, not true ASIO). As to flipping channels, generating mono, etc. all that and more can all be done with Channel Tools in the master bus which is more flexible than opening another app. I'll alert TASCAM to this thread, but so far you're the only person who's reported this and I can't reproduce; I don't know if there's sufficient info in what you've posted to let them make an educated guess as to why it's not working on your system. As I said, I can have SONAR playing back audio and several Windows apps playing back audio and it's all fine. The only time I could experience what you're experiencing is if another driver is installed. (However like CactusMusic noted, there may be sample rate issues and in that case, all bets are off.) 
 
Finally, note that some interface drivers simply will not work properly if ASIO4ALL is even installed in a system. I can't verify if that's the case with TASCAM because I keep ASIO wrappers as far away from my system as possible. This forum is littered with posts from people who experienced weird SONAR or interface problems, and uninstalling (not just turning off ) ASIO4ALL solved them. I presume other wrappers might be subject to similar issues. But again, everything is working fine here so I have no real incentive to investigate further. Maybe TASCAM will have some advice they can give you.

Etostone
ps. audio4all and another asio wrapper didn't worked with the tascam. 

Anderton

Etostone
ps. audio4all and another asio wrapper didn't worked with the tascam. 

I just noticed this. Are they currently installed on your system? That's the kind of information TASCAM would need to know. TASCAM may be one of the companies whose drivers will not perform properly if ASIO wrappers are installed on a system. 
 

Anderton
I just sent off the thread URL for comment. I'm still confused as to why I can play as much audio as I want, including SONAR running ASIO and Windows running multiple sound sources, and you can't. I don't know what difference in our systems would account for that...maybe TASCAM will be able to reproduce your issue and report on a solution.

TomDuffy
At Cakewalk's request, TASCAM has been looking into the reported behavior.   We have identified a problem and are working on a solution.
 
Tom (TASCAM)
 

TomDuffy
Recap for TASCAM support - for customers in North America, please use the page here: 
http://www.tascam.com/contact/support
 
This _will_ generate an auto-response email with a unique Reference number in it.   If you say "I never got a reply", we need you to supply that Reference number so we can look up the conversation.
There is also the phone support line for North American customers. 323-726-0303 ext. 617 (M-F, 8am-5pm Pacific).    Our guys are regular users of our gear, so they can usually spot the hiccups people run into.
 
For customers in the UK, there is this page:
http://www.tascam.eu/en/support-uk.html
 
For the rest of Europe:
http://www.tascam.eu/en/supp_interfaces.html 
 
These two are not as automated. The TEAC EU staff rarely drop things, but they may need more time to research answers.   Things that don't seem right normally reach me through these channels, but we do not read all the forums directly, so we need you to tell us directly what problems you are seeing.   Of course linking in a support request to a forum discussion is fine for providing background.
 
For elsewhere in the world, find the correct email contact by starting here:
http://www.teac-global.com
 
If it comes down to "we're not sure what's going on", we have to wait to see if a similar thing occurs for other users before we can see how to divide and conquer.  Accurate information always helps.
 
Tom.
 

Anderton

Etostone

TomDuffy
For elsewhere in the world, find the correct email contact by starting here:
http://www.teac-global.com
 
If it comes down to "we're not sure what's going on", we have to wait to see if a similar thing occurs for other users before we can see how to divide and conquer.  Accurate information always helps.
 
Tom.
 

I already did this. My reference is > 
Reference: ECIFKJ72
 
When I tried to send more information to the same email : Array@aws.teac.com
the email bounced back to me writing that "can't deliver cause time out" !
Now If I cant send emails to Tascam how possible I could help them to fix the drivers ? 

 
I just sent a test email to verify that address and did not have any problems. It was sent and delivered. [EDIT: A couple hours later, I received an "email delayed" reply. So it does look like there's an issue. I will alert TASCAM.]
 

Also I just found a new problem . that after 8-10 hours of my PC computer running continuously , the audio is disabled by it self. 
It seems that there is a power in problem with the rack interface.  Then I have to turn off and turn on the rack to get sound back , but it will only work for 10 mins. I have to shut down the PC and then turn it on to get back to windows for a completely fresh reboot and to get audio back for another 8 hours session. 

 
I don't know why you have these issues. I run my US-4x4 for hours without problems. But if I'm running for hours that means I'm just using SONAR, not switching back and forth among other programs. I assume you have all your USB ports set so they don't suspend power.
 
As Tom says, "we have to wait to see if a similar thing occurs for other users before we can see how to divide and conquer." Only then can they see a pattern develop that relates to the interface as opposed to its interaction with a particular system.