I normally have LoopBe30 configured with one internal MIDI port in Sonar, so it activates when I launch Sonar, and it stops when I quit Sonar. Sonar had crashed on me the day before, and it turned out that LoopBe was still active. I had to reboot to clear this up.
I discovered this issue when I was trying to figure out why my PC was not sleeping yesterday. I have my PC setup to sleep after 60 minutes with no activity.
If you run a Windows cmd prompt as administrator, and enter "powercfg -requests" you can see the drivers and devices listed that can keep the computer awake.
Yesterday, I saw this even with Sonar shut down, and as a result my PC would not sleep:
C:\WINDOWS\system32>powercfg -requestsSYSTEM:[DRIVER] nerds.de LoopBe30 - Internal Midi Ports (WDM) (ROOT\*LOOPBE30\0000)An audio stream is currently in use. I guess that this can mean that when Sonar gives the error "SONARPLT.exe has stopped working", it may not have time to clean up everything.