Where did the audio clip labels go?

Hi all:

I'm developing a course with six interactive modules. I've been setting up a separate project for each module and plan to add links when I'm done. In the meantime, I'm working on each one separately.

In the modules I've worked on up until now, a label appeared over each audio clip when I rolled over it in the timeline, displaying the title I gave it when I saved it; for example, when I roll over a clip I titled "7-dimenions.mp3," that title appears. 

This was very helpful, because I have re-recorded many of the clips and replaced them as I've gone along. Seeing the title on the label lets me know I'm replacing the correct old clip with the correct new one. 

But the rollover labels are no longer showing up in any of the modules. 

I assume I must have inadvertently changed a setting somewhere. 

Anyone know what this is about? 

TIA - 

Lerissa