There used to be a switch in preferences that allowed drivers being used in sonar to be always shared...I cannot find this now...is it in a different place?
 
Thanks

The option is in Preferences->Playback and Recording
 
If you're using WASAPI, then pick "WASAPI Shared" as opposed to "WASAPI Exclusive".
 
If you're not using WASAPI, then checking the "Suspend Audio Engine When SONAR Is Not In Focus" should disable the audio when you switch to other programs (e.g. a browser). Not all audio drivers may respond to this though.
 
M.

There is also a set of "Exclusive Mode" check boxes in the Windows Sound Card Setting panel under "Properties" for a device and then the "Advanced" tab. If sharing drivers, you may want to uncheck those as well.

Under shared mode only the program that has focus in Windows has access to the ASIO sound card.