I have run into a problem with playback of my  projects. Project will start but when I stop it  it freezes and stops responding and I have to close out of the program.  It will happen on any projects. Even the ones with just midi.  I'm using a Focusrite Scarlett 6I6 interface (USB) and have installed  latest drivers. I have also reinstalled Sonar.
I don't believe it to be a virus. I don't use the internet with this laptop.
 
Have not had this problem before and I'm a musician with a gig on Saturday night. Would appreciate some help!
 
OS is WIN 7.
Processor Intel(R)  Core(TM) i5cpu m460 2.53 ghz
RAM 4.0
64 Bit

Hi. Have you tried a different USB port / cable? Are you using any fx, that could be causing trouble? (I had issues with NI Replika 1.2.1, but disappeared after updating to 1.2.2, as an example) Which Vsti are you using?
The more you tell about your project / problem, the easier it will be for people to give you an answer.
Best of luck.

Have you tried any new VSTs?
I recently noticed that Addictive Drums (1) and Orange Tree Steel Strings Guitar don't like eachother,
especially if AD is loaded with all outputs and even if the extra output tracks are then deleted.