I have used the line in on my mac pro for recording, and to take the sound from my Wii to my stereo so I can listen to iTunes at the same time. However, my line in seems to have inexplicably broken. Suddenly, nothing shows in the sound system preferences or in "line in" application. I've checked the obvious, cable inserted properly, different cables, different sound sources, restarted, fixed permissions (don't know why that might help, but worth a try). Would running the hardware test show any hardware problems of this kind? Has anyone else had this problem? Or, more importantly?, any ideas how to fix it?!