Audio error message in VErs. 6.2.3

All audio files are now showing the following error message:
This problem occurs since version 6.2.3.
Vers. 6.2.1 does not cause any problems with the audio files.

Loading the media file during playback took too long. The correct timing of the slide show could therefore not be maintained.
You could replace the audio file with a recoded version using a different audio codec.

What does that mean and what do I have to do specifically