I figured it out. This information should probably entered into the Knowledge Base, or made into a sticky post at the very least.
 
Problem: Sonar hangs during splash screen initialization.
Cause: Sonar detects ASIO audio card drivers and attempts to connect. If the unit is unplugged, or off, with no phantom power supply, the connection will be left open and unanswered, thus causing the hang.
Solution: Plug the unit in and turn it on!
Recomendations: Update Sonar to utilize a timeout on such connections and automatically re-calibrate to something like WDM or another preferred secondary interface. This is, of course, a development issue.
 
I figured this out by taking the advice above and uninstalling the ASIO drivers. But before I re-installed them, I attempted loading Sonar again. This time it worked. I installed the drivers again and reloaded Sonar, only to have it hang again. It occurred to me that, as I was setting up a new system, and had not moved my interface in to the room yet, I should do that. Once I did, Sonar loaded with no issues.
 
Thanks for all the input and dialog. Hopefully, this will help somebody else in the future.
 
Cheers, Drew

Which audio interface are you using? Its not normal for the driver to hang if the device is missing. I suspect its throwing a dialog but the dialog is not visible hence it looks hung. SONAR itself doesn't hang when a device fails to load so there is nothing to fix from the SONAR side. 

Hmmmm...if an interface isn't connected, for me SONAR has always just loaded Windows audio drivers. Check the taskbar and see if the splash screen is there, but hidden behind SONAR.

It's an old M-Audio Fast Track Ultra, which was sold by the company to Avid I believe. I also get the impression that their updated Windows 7 drivers are not all that professionally written. It is probably the driver that is crashing the system when an attempt to use it while not connected is made. It doesn't really seem to be a Sonar issue at this point, however, there should be a way to write a safegaurd around this with a multi-threaded process.
 
If not plugged in, it definitely hangs, invoking the "Not Responding - Check for solutions" dialog. I haven't actually tried with it simply turn off, but still connected.
 
There are no hidden dialogs listed on the bar, or in Apps / Processes in Task Manager.
 
Any other input you guys need?

I just launched Sonar Platinum using my FastTrack Ultra and it worked ok.

gswitz
I just launched Sonar Platinum using my FastTrack Ultra and it worked ok.

Mine does now too. Now that I know it has to be plugged in. For some reason it didn't work when unplugged. Curious, what driver are you using? The one that came with, or the updated one from Avid? And what OS are you using? The more info we have, the better.

I'm using Windows 8.1.
I always plug in my interfaces so they don't need to get power via USB. If your USB Bus is under-powered, you'd have trouble with your interface.
 
Firewire carries more power, so Firewire interfaces sometimes work well without being plugged in.
 
I can add that back in the day, I used to use a couple of channels on the interface without it being plugged in - when using a laptop to do recording.
 
I use the latest drivers from here for the FastTrack Ultra...
http://avid.force.com/pkb/articles/en_US/download/en379411
 

Oh! When I said "not plugged in", I meant "at all". Like, the USB itself isn't even hooked up.

I will say the pre-amps on my FastTrack Ultra went bad. It maybe the case on yours too. Bump the buttons on the front to switch to the rear of the interface. Use external pre-amps and see if that fixes things for you.
 
if you are using it USB Powered, definitely switch to Rear for all channels not in use to bypass the pre-amps.

I just encountered this condition under Windows 10 with Sonar Platinum. My main audio device is a MOTU 8-pre USB which works fine. I am using an Alienware Laptop. Sonar started hanging at startup after latest Sonar maintenance install. Could not even kill sonar task via task manager. I then disconnected my Targus USB 3.0 port replicator, and Sonar startup completed. Sonar was hanging trying to detect or process the audio device built into the Targus USB 3.0, which I don't use and have no audio cables plugged into. Latest Targus drivers installed, and on latest Windows maintenance. For now, I unplug Targus before starting Sonar, and then plug it back in after Sonar initializes. Disabling Targus audio device in device manager doesn't help. Perhaps someone at Sonar can recreate this issue and bullet-proof Sonar from hanging on audio device detection at startup?