If you are using the interface for everything, then the advice above to "share drivers" and using WDM mode should work.
 
In Win7, if you click the Start button, there is a text box just above it that will appear. You can type "sound" in that and select "Change sound card settings" from the list. When in that, if you select your interface and click the "Properties" button, a pop-up will come up. On the "Advanced" tab, make sure that "Allow applications to take exclusive control of this device" is unchecked.
 
Also, within SONAR, if you go to Preferences->Audio->Playback and Recording you will want to have "Share drivers with other programs" (near the top) checked.

OK I think I've got it now...i'll wait & see what happens. Thanks for staying with me.

As far as I know, I never use Sonar at the same sample rate in my music as everything else that runs on the Internet or Utube or whatever. That is 44100 Hz sample rate. In Sonar I am always using 48000 sample rate or now trying 96000 sample rate. Although with my unit, it seems to work, I tend to never share drivers in Sonar because in Windows 7 in Playback Devices -> Properties I have on the Advanced Tab the checkboxes checked that says Exclusive Mode - Allow applications to take exclusive control of this device (which is the Default I have marked as the playback device which in my case is not Speakers but Headphones) and also checkmark -> Give exclusive mode applications priority, which are both Windows 7 settings for or in the Properties of my Default playback device.
 
But then I usually am listening to utube or whatever (WMP) and not using Sonar at the time anyway, since I always record in something different than 44100 sample rate and rarely record in that sample rate.
??
I know I have forgotten sometimes to change the sample rate on my device and ended up having 96000 as the sample rate sometimes, but the only time it seems to bother anything is if I try and change the sample rate back to where it should be I think which is 44100, and do not shut down the program or the website I was listening to. If I do not, then a problem will happen which is like the interface not working right and loud noise on channels that should not have it to the point of actually shutting and restarting the computer back up because I tried to change it on the fly.
 
 Windows is never going to use anything except its drivers which are the WDM/KS drivers while in Sonar I never use anything except ASIO drivers.
??
Usually I tend to switch the sample rate back to where it should be before starting either program (Sonar or WMP or listening on the Internet) which to me always should be done.
 
Also like Robert E Bone stated in his post.
 
 

+1 that is another good point to check, since applications may create their own issues by not supporting the audio format the interface is set to. CD quality (16 bit/44.1KHz) is about the only "universal" which is not preferred to use within SONAR (why most people deliberately leave SONAR exclusive).

Well, I found out some other stuff. But do I understand it? Nope not yet, but here it is, about how things changed from Vista On (Windows 7, 8 etc) in the OS with audio.
http://msdn.microsoft.com/en-us/library/dd370844%28v=vs.85%29.aspx
 
Ah, now back to taking aspirin.
I assumed I knew what Windows was doing, but now, I am not sure. I am just sure I have 44100 24 bit marked in Windows for playback when running in shared mode, but then I really don't want anything running in shared mode, as far as I know. The rest will have to be read about maybe a couple of times. It has to do with how the the program is programmed. And as far as I know anyway, streaming over the Internet always I think uses Flash so that is to me different than a program like WMP playing anything or maybe SimAmp whatever program.
I am thinking I do not use WASPI whatever it is mode but with that, if bit rates and sample rates do not match I am thinking (or trying to remember after reading the article) Windows OS changes that to match what you have marked on the Advance Tab where it says do you want 44100 24 bit or 44100 16 bit above the Exclusive Mode stuff.
Anyway, if not using that mode then I think Exclusive mode give the program the option to stream music how it wants to, but if not matching then there will be silence. The only thing I got so far is that WASPI whatever it is called, is Windows own version of ASIO drivers or so they said. In all there is latency involved with using audio/interfaces and any of that and some of the reasons Windows OS changed things starting with Vista after XP with audio (and probably something with video also.
 
well, back to the headaches trying to decipher what is going on I guess.
??
From the link:
"In Windows Vista, the default settings for an audio endpoint device are the following:

• The device can be used to play or record exclusive-mode streams.
• A request to use a device to play or record an exclusive-mode stream preempts any shared-mode stream that is currently being played or recorded through the device."

That would include any future OS like Windows 7, 8 whatever.
To me that means using Exclusive mode in Windows marked by those checkboxes, means that whatever is the software being used (not in the background but in the foreground as in the windows of the program) for playback or recording gets the priority while shared-mode would not do that.
 
 

ya, I just put my audio/interface at 96000 sample rate, and then opened up WMP and played a song I know is in 44100 sample rate and probably 16 bit. Nothing happened, nothing exploded, the song played fine, even though my audio/interface was set at a different sample rate. I think the same thing has happened on the Internet with Utube when I have forgotten to change sample rates back - using Exclusive Mode checkboxes in Windows Playback devices for my Default playback device.
 
But switching while running will screw things up where I have had to restart my computer when messing up that way or else loud noises from channels in my audio/interface (like ADAT) in software playback section don't go away until I restart my computer up for messing up.
 

Same thing with the Internet and a utube video I have up. Nothing happened, just played back. (probably also because they only stream at 128 bits like an *.mp3 file anyway unless HD which is suppose to be 192 bits like an *.mp3 file.
 
However to me, it just does not seem right to do that though. Now I am not sure whatever is playing back is playing back at the sample rate anyway but should be if set correctly, except in Sonar, Sonar works right.