When playing, Geek Perfect will take over exclusive access of the output device (known as “hog mode”). Even if Geek Perfect is paused, the lock is still in effect.
Check the Geek Perfect icon in the menu bar at the top of the screen to see if it is green or black. If it is green, it is playing or paused. If it is black, it is stopped.
To release the lock on the output device, go to the Geek Perfect menu and select Stop, or Quit GeekPerfect.