Sonar Platinum with Focusrite Audio I/O (tough problem)

I have two Focusrite interfaces. One is a Saffire Pro 24 (connected via firewire) and a Scarlett 2i2 (connected via USB)
I have been using the Saffire Pro 24 for quite awhile (along with the Saffire software Mixer) without any problems.
But recently I've been getting issues with the Pro 24.  For example, after I closed out a session of Sonar, I'm unable to hear any streaming audio or any audio files on my computer.  If I reboot, then I sometimes can hear them.  There are other issues the interface was causing, but I won't go into all those details right now.  I used to be able to listen to streaming music from the Internet while playing along in Sonar at the same time.  But now it's only one or the other at a time.

So I switched back to my older Scarlett 2i2,  I downloaded the latest drivers and files.  It seems to work fine on both streaming music and audio files on my hard drive.  It even works in Sonar.  But whenever I open Sonar up,  I get the message that there is no Output Device connected.  And when I go to MIDI Devices, there is no Focusrite device listed there.  The only outputs it shows are, Microsoft GS Wavetable synth, Oxygen 88 (my midi keyboard, input only), and Game Controller 1.  There is no Scarlett 2i2

If I close the preferences box, and open up a project, I DO hear the audio coming out of the speakers, and headphones.  But I'm not sure how or why.   None of the three listed output devices are checked, and yet I'm still getting audio.

I am able to record with a microphone using the Scarlet 2i2, so I know the USB connection is good.  It's just that in the preferences there is no listing for that interface.
I'd really like to go back to the Pro 24 firewire interface. (I read that Firewire connections are better than USB)  But now it seems both aren't working as they are supposed to.  There seems to be some conflict with Sonar and all the other audio I use on my computer.

Any suggestions or ideas?  Thanks!

SONAR is constrained by what Windows is controlling. If you check your sound cards in Windows ("Change Sound Card Settings") by highlighting them (one by one) and then "Properties." In the Advanced tab, I have both "Exclusive Mode" options unchecked. This will allow applications (who have the ability to assign exclusive modes) to function properly, but I leave those unchecked as well. I also leave my onboard Realtek as the "Default device" so instances like a browser streaming audio does not "lock" the bit rate on it... that feature is is "first come, first served" so if an app locks the Saffire at a given bit rate/bit depth, it will not be able to stream other audio.
 
If you use it the Saffire for general purposes, I would also set the "Default format" on the Advanced tab to what you normally run SONAR at to avert potential conflicts (since Windows will pretty much be using it (and lock it) before SONAR can see it).
 
Windows can potentially reset those properties on an update, so they may require re-visiting from time to time.

I'm currently using a Safire Pro 40 on win 10. I haven't really had any issues with it, but I noticed a while ago that it stopped being so good at letting go of Sonar when switching to other sources that are at a different sample rate. Most of my projects in Sonar are at 48k where as most stuff in windows is 44.1k.

Re Mettelus' post, with my Focusrite 18i20 2nd gen, exiting Sonar could change my listening sources until I created profiles with Focusrite mixer working in tandem with Windows mixer re realtek HD, others, and I listen to YouTube, internet radio, etc simultaneously no problems.

I used to have a similar issue, suddenly there'd be no sound from the interface (not a SONAR issue). The problem seems to have since gone away on its own, so I never figured out what was causing it. But here's a tip for bringing sound back if it happens again: rather than rebooting, just open MixControl and change the buffer size. That forces the interface to re-initialize itself, and for me has always brought it back to life.