1 - If I insert AD2 synth using the browser all works well until I take the focus away from sonar (say, click on a word dock or just the desktop). Returning to sonar it either crashes or wont play ANY SoftSynth at all even though the track/Bus meters indicate audio is present and Preferences Drive Settings tell me the drivers for my Quad are still present.
 
2 - If I insert AD2 in a track Fxbin then it works fine when I switch between focus away and then back to Sonar.
 
I'm baffled at this. Help please

Oops spoke to soon, now this behaviour happen regardless of how I insert AD2.
 
I'm now more confused then ever! 

Maybe a driver sharing issue. If Preferences > Audio > Playback and Recording "Share Drivers With Other Programs" is enabled, uncheck the option.