Anybody know why the waveforms in various audio clips might keep disappearing, and turning into straight lines?  On many tracks, the waveform in a frozen track disappears upon opening up the project, but can still be heard.  The clip displays straight lines where the wave was.  If I Unfreeze the track, the wave shows back up.  Then I refreeze.  But on tracks with multiple takes, some clips never redisplay their wave, but yet can be heard.  Next time I open the project up, the wave may or may not display.
 
This problem is unpredictable and varies each time I open up the project.  It's annoying, as I really need to see the waves.
 
Any advice greatly appreciated.

Try clearing the picture cache.

In addition to get the waveform back, right click and select Associated audio files and then use "Recompute Pictures"

Karl-  That did the trick my friend!!  Many thanks!

Now tell me how to change the title of my thread to include the word "SOLVED"....  LOL

In my case I'm getting random horizontal black lines spread in various places amongst the tracks. Resizing track hight/width doesn't clear them. I had this problem many versions ago. Did not update any video drivers to cause this.

KEv