Output switches when system line-out connected or disconnected

Cog 0.07 (r635)
OS X 10.5.5
MacBook Pro ~2 years old

Using Cog with the output device set to a Griffin iMic, the music will switch to the built-in output if the system line-out is either connected or disconnected.

Steps to reproduce:

1. Connect iMic to computer
2. Connect iMic output to some listening device (I use headphones)
3. Start Cog
4. Set Cog output device to iMic ("iMic USB audio system")
5. Start a track playing in Cog, which will come through the iMic output
6. Connect some listening device to the system line-out/headphone jack

At this point, you should hear the Cog output through whatever was just plugged in. And if, like me, you're using a computer with built-in speakers, unplugging the listening device connected in step #6 will then have the Cog output go to the built-in speakers.

You can get the same result if you start with a listening device connected to the system line-out/headphone jack and then remove it in step #6. At that point, you should hear the Cog output through the built-in speakers.

Finally, the selected output device is still listed as "iMic USB audio system". To get output back to the iMic, I have to select something else and then re-select the iMic.

Note: I looked through the forums and tickets and couldn't find any mention of this. And I wasn't sure if I was supposed to create a forum topic or a ticket.