Found my solution to the exact same (Sonar hanging at splash): Deactivated all audio devices I do not use in the device manager of Windows. I had things like a USB Dock audio device, NVIDIA Audio devices etc there. Deactivated all but the one I need ... and voila, it finally starts up right. 

FYI, Sonar support:
This issue still exists on Sonar Platinum 2016.04 level - and is easily reproduced. Install a Targus USB 3.0 port replicator with no audio devices attached to it. SONARPLT.EXE hangs solid at splash screen - reboot is only way to break out - task manager kill has no effect.  Only circumvention is to disable Targus USB Audio in Device Manager.
Windows 10 user with Sonar Platinum.
 
 

I am trying to demo the Sonar Platinum and it poofs after splash screen shows for 1 second.
 
Everything else is peachy on my Windows 7 here.
 
So I tried to uninstall but it doesn't show in the Programs and Features.  How do we uninstall?

Found the same solution as mdfmike - makes no since to have to unplug usb interface and plug in after initialization something need fixing - lastest install on Tascam 2x2 - will not install on main system Tasam 20x20 until this is fixed - still using X2 Prod on main