1) Start Podtrapper
2) Go to the "play screen" (with the icons for play, ff, rew, etc.) of the last played podcast (or a new one)
3) Invoke the Podtrapper keylock (press L)
4) Press the Mute button to play the podcast - it won't work!
I found that I need to play/pause the podcast first using the trackball or the spacebar before locking the screen for the Mute key to be enabled.
This is only an issue when you first start Podtrapper.