I'm bumping this thread because the issue is back. I made a post on the Microsoft forum and haven't gotten a reply to help me fix the issue. I know that this isn't present in FL Studio, so it is an issue with Sonar and Windows. I'm assuming Windows is somehow viewing Sonar as a media application and it's using the plus and minus keys as shortuts to control the system volume.
I've searched high and low trying to find a system settings or option to fix this problem. I've even gone into my keyboards software and turned off all Fn (function) controls and that didn't help. Would be nice if someone around here can chime in and help both Kamikaze and myself stop the plus and minus keys from controlling system volume while using Sonar.