I have a very simple project with a couple of soft synths loaded.
Motu ethno and Motu symphonic.
I try and turn the Input/Echo off on the Symphonic track but it still sometimes echos (this has not happened before)
After fiddling like freezing it to get it to stop echoing, I can finally play my second track the Ethno instrument.
A few clicks later and I get the blue screen of death.  This is unlike Sonar, its been pretty stable for me.
 
Anyone got any ideas?  Maybe I should start a new project?
 
(Win 7 64 bit,  Sonar Home 6XL)
 

Blue screens of death can be related to CPU overload. Are you overclocking yours by any chance?

What's the BSOD error, not all the numbers, just the code text like:
IRQL_NOT_LESS_OR_EQUALWhich is just one of the many on the BSOD hit parade.
You can generally glean what may be wrong by googling the code text.

Does this happen on all projects or just the one? Do any projects with the motu Synths inserted have stable playback? Do projects with other synths inserted play back without issue? 
Just trying to ascertain whether it is a particular element of the project or just system load that is causing it to fail. 
 
Did anything change on your system with regards to hardware or software updates around the time that this problem began? 
 
Also,  if I recall correctly (it has been a while since I tried  it)  motu symphonic is a 32 bit plugin.  There is a 64 bit version of the symphonic library that  you can play using a 64 bit host that would be a better way to go.  32 bit plugins on a 64 bit system are best avoided for greater stability. 
 
 
I had an intermittent BSOD that seemed almost random that turned out to be a bad RAM module,  despite it passing all ram stress tests  etc. Certainly not saying that is your issue - so many things have the I'll fated BSD as a symptom. The more variables you can isolate the better. 

Thanks, I did note the message when the BSOD happened.
It said,  BUGCODE_USB_DRIVER
Now that I think of it, I just installed ASIO4ALL.   Perhaps that is causing the issue.

MrBansaw
Now that I think of it, I just installed ASIO4ALL.   Perhaps that is causing the issue.

Definitely ASIO4ALL is the first thing I would get rid of...... As your UA-1EX usb audio interface is ASIO compatible and a driver is available for your OS (Windows 7 64bit) , you do not need ASIO4ALL. Also, make sure you're using the latest driver for your audio interface, available from here: http://www.rolandus.com/support/by_product/ua-1ex/updates_drivers/

I don't see that bsod much but many sure have:
 
https://www.google.com/se...;ie=utf-8&oe=utf-8

+1 to get rid of asio4all driver first. That said bsod is a pretty extreme symptom even for dodgy old asio4all. Not beond the realm of posibility though, and either way you are far beter off without it.

 We should flog all of those who think ASIO4ALL is better than manufacture drivers and flog developers whose drivers are worse than ASIO.  The would exclude RME.

I was seeing this error a couple of years ago. Turned out to be caused by a defective USB hub that had nothing related to audio or MIDI connected to it.