Jean, the green fill of the clips indicates that DaVinci sees the files on your hard drive. Otherwise you would see the red missing media icon. So, the only thing that comes to my thought is that the files are corrupted. One test is to open the source files on the hard drive and see if they play outside of DVR. That would indicate if the source files are corrupted, or not.
Assuming you have original copies of the audio clips, have you tried to delete them from the drive and folder location, and re-copying to the appropriate DVR folder and re-linking the files?
Is your hard drive running directly off the motherboard, or is it on a USB drive or a network drive. Possible that it’s a cable problem or hard drive corruption.
Possible, but not likely, that DVR is corrupted. You could try re-installing DVR.
Sorry, that I’m guessing here, but those are my ideas for isolating the problem.