I have an issue where the playback or midi control stops when I change windows or minimize the Sonar window.
Is there a magic checkbox somewhere that I can't find that will fix this?
 
System:
Dell Studio 540
Windows 7 Pro
Sonar X1 Producer
Line 6 Toneport GX (functioning as soundcard)
 

here are a few things to try, try these one at a time:
1. Use the ASIO Line 6 driver in Sonar.
2. It seems like your audio driver is being used and not returned by something else when Sonar is not the focus of attention. Try turning on (check the box) "share drivers with other programs" in the Sonar options.
3. Another thing to try is turn off system sounds in windows. Use the "No Sounds".
It could be that the driver is being taken by a windows sound event.

One possible reason for this, could be that "Share Drivers With Other Programs" in  Preferences > Audio > Playback and recording is checked.

If it is, just uncheck it.

That worked! Thanks!