Sent message to Sonar tech. They sent me to Tascam tech. Sent message to them on Monday: NO response.
 
Meanwhile, back at the ranch: I installed the 16x08 on another AMD based computer. Installed the latest sonar version and SAME results: immediate drop-out and error about device not found.
I could still use the media player and play youtube vids, with sound just fine.
 
Yes,  ASIO was selected in sonar.  Sonar found/finds the device correctly.
 
Today I installed a new USB card because a Tascam tech told another poster to do this and it fixed their problem with noise.
Installed a Mailiya PCI-E to USB 3.0 2-Port PCI Express Card, with NEC chip.
I uninstalled the 16x08 driver, restarted, and installed the driver, restarted. (Did not update to 2.1)
I tested with media player and videos: all good.
 
Loaded sonar and NO JOY. Same dropout and error. AND:::: the windows error sound was heard by all.
 
Again, i send a message to tascam. 
 
This has been a very unhappy experience. A waste of time, and lost income after the OS disk refused to boot after uninstalling the driver. (See details below if you have any interest whatsoever.)
 
I am prolly not purchasing a tascam product again.
 
Way too many messages everywhere about problems with these devices, including lots of sonar users who gave up. I should have read more before wasting my time.
 
======================================
 
 
UPdate: After the problems below, i uninstalled the tascam driver and the OS disk became poop on a rope.
No way to fix it. So i started new: fresh w10 anniversary install and all updates.
I installed the tascam software. Could play youtube vids, sound was fine.
BUTTTT:  the computer would not boot with the tascam powered-on.
It worked after the computer was booted.
I installed the latest CCC and sonar and a few other bits.
I started Sonar, it found the tascam and then I attempted to play a tutorial file. It loaded fine.
Immediate audio drop-out and display of error: audio device not working, or some such.
 
I have thought the motherboard USB ports were sometimes strange before i attempted to installed the tascam.
So, i updated the bios for the MB: an fix for some USB 3 stuff.
All went well, except the OS disk was not bootable. (The disk is fine, removed tested,... not the disk)
 
So, again i do the OS fresh install thang.
I install the tascam, it works fine.
I change the windows audio settings to prevent programs from claiming total control.
I install the CCC, and the latest sonar.
I load a project, and audio dropout.
 
And the computer will not boot with the tascam powered-on.
 
Current system: Gigabyte 970a-d3p, AMD fx-8320, 8 gigabytes ram, three disks
 
Any ideas to fix this?
 
Getting ready to order new Motherboard.
 
 
=================================
Just finished installing and updating a tascam us-16x08 interface,
 
sonar crashes on opening. I have restarted. I have change the windows audio settings.
 
Any ideas?

By updating do you mean you updated the Tascam firmware? 
 
So your saying the Tascam shows in Windows as your audio device? 
Did you find a Tascam icon in control panel you can open the GUI and set your buffers?  This will prove the Tascam is up and running properly. Play some music with Media player. 
If tall that is good then it narrows things down to Sonar is not happy for some reason.
 
You did re start your computer?  

The interface is working. Videos play fine.
 
 
Did a firmware update, and installed the latest panel.
 
Sonar Plat displays the splash screen and then nuttin.
 
 

Is the Tascam showing as the only audio device? 
What other audio devices or drivers have you installed. 
Asio4all and Creative as example can cause this to happen. 
Uninstall and/or disable all other audio drivers including HDMI audio in device manager. 

Thank you for your questions,
 
The Tascam was working fine. Playing videos and testing system sounds. All good.
 
I did remove the software for the old audio devices. They were not loading but now all gone.
 
Sonar would display the splash screen and then hang.
 
After the 10th restart from installing and uninstalling, I uninstalled the Tascam software, and some old unused programs.
 
Unfortunately the machine would no longer boot. Tried some repairs this morning but noooooooo.
 
So the OP is sorta moot until I get the comp working.
 
 
 

At this point you should maybe give more details of your system specs. We don't even know what OS your using. 
Possibly you have a hardware issue and that was the problem to begin with. Possibly your OS drive. 
Can you open the Bios and check if your OS drive is active?  
Open the case and check all the connections. I just moved a computer the other day and lost my data drive. It was a loose connection. 
 

I couldn't get the ASIO drivers supplied with my 16x08 to work with Sonar either.
WDM works, so now I just use it for playback and mixdown work.
 
The ASIO drivers work fine with Reaper and other audio software. Just not with Sonar.
 

Well your doing something wrong because many people here are using the US 16x08 with out issue. After all Tascam and Sonar are owned by Gibson and my guess is they use Sonar to test the interface drivers. 
 
Edit: I was wrong here, now I'm seeing reports of issues with this one interface.  

http://tascam.com/content/downloads/products/859/e_us-16x08_fw-update_va.pdf
 
http://tascam.com/content/downloads/products/859/e_us-16x08_rn_vd.pdf
 
And you should be using Driver 2.00 released in November. The seem to have changed the driver to a combo pack like Focusrite does. You get the driver and the control panel update in one download. 
 
You need to follow install direction very carefully when doing firmware updates.
 
And if it's like my Tascam don't turn the unit on or plug in the usb cable until it tells you during driver installation or it won't work. 

I have two Tascams, US-122mkII and US-2x2 (side note: the 122mkII gives me less issues then the newer 2x2) and the both required to be installed as Cactus said:

Cactus Music
And if it's like my Tascam don't turn the unit on or plug in the usb cable until it tells you during driver installation or it won't work. 

Doubt this will help your situation, but with my older one I had to install the CD version that came with it, then Sonar worked (this was with X2 or 3, can't exactly recall). I could then update to the latest version, including the firmware...must have been a lunar alignment issue