Audio Waveforms won't display in Viewer or recreate themselves

Okay, I don't know what happened. I've been cutting a film with FCP 6.0.6 and Lion, using a TBD to access my Firewire 800 drive. So far, no real problems, other than screen tearing (probably because I'm using a Macbook Air - it's a long story, so please don't hate on me for that.) Suddenly, my AUDIO WAVEFORMS have vanished from the Viewer. I trashed prefs, etc., restarted, same problem. I read somewhere about emptying the Waveform cache so I did that. (Just in case, I haven't emptied the trash though). I thought FCP would simply redraw and create new waveforms upon opening, and double-clicking files to view audio in the Viewer. But not the case. Just a white screen with the play line. My keyframes are visible. No x's. And no waveforms. I checked the Waveform cache, the folder remains empty.

What to I do?

Chris