I get the same exact message on my desktop from time to time when I unplug my main Montage M7 controller or unplug my SSL audio interface. Though it is a strange thing, it ALWAYS rights itself simply by unplugging/replugging in the sound card and rebooting, and sometimes I have to check in the preferences like you're doing a re-select the right driver or audio card. It's a flaky sonar cakewalk thing. Happens to me more than I would like. If you're only moving your project/bun file from one pc to the next, you should NOT get any message like this at all. One pc/the other laptop have nothing to do with each other unless...you're unplugging your interface from the main pc and taking it to the 2nd location. So what I suggest is...do not turn the 'other' pc back on until you plug your soundcard/interface in FIRST. This way you might be able to trick Sonar into thinking it never left, was never unplugged. Bottom line is, this is not a serious issue. "UNABLE TO OPEN PLAYBACK DEVICE" simply means sonar can't find, for some reason, your interface. It has nothing to do with sample rate, and that other stuff. I get the message from time to time, and within a few minutes of unplugging, replugging, rebooting, checking 'preferences', I'm good to go. Again....to trick your pc's...make sure everything is plugged back in BEFORE you start the 'next' pc...plug everything back in, just like when you left it, THEN turn on the pc, then open sonar. Same in reverse. When done in one room, close sonar, shut the pc down. Move your interface to the 2nd room/pc, and while it is OFF, hook everything back up. This is not a 'deep' issue. That error messaage is common. SOMETIMES you may have another device using your interface/set up to use it, and you don't have your preferences set up to 'share'. And you do NOT want to use ASIO4all drivers, ever. In my case, 'realtek' drivers always want to take over Sonar, even when I disable them outside of DAW. That message just means Sonar/DAW/PC is not 'seeing' the right sound card, or its in use elsewhere, and it's tied up, not available to sonar. It's really that simple. But yes, it is frustrating when it happens and you do have to monkey around a bit to solve it. But...if you notice: You probably get the same error message several times, not just this once? So that means, Sonar eventually DOES see the soundcard, and you're back up and running. Don't need to change all those internal preference settings. Those are not the problem.